As we age, our brains change, but Alzheimer’s disease and related dementias are not an inevitable part of aging. In fact, up to 40% of dementia cases may be prevented or delayed. It helps to understand what’s normal and what’s not when it comes to brain health.

Normal brain aging may mean slower processing speeds and more trouble multitasking, but routine memory, skills, and knowledge are stable and may even improve with age. It’s normal to occasionally forget recent events such as where you put your keys or the name of the person you just met.

Symptoms of Dementia or Alzheimer’s Disease

In the United States, 6.2 million people age 65 and older have Alzheimer’s disease, the most common type of dementia. People with dementia have symptoms of cognitive decline that interfere with daily life—including disruptions in language, memory, attention, recognition, problem solving, and decision-making. Signs to watch for include:

• Not being able to complete tasks without help.
• Trouble naming items or close family members.
• Forgetting the function of items.
• Repeating questions.
• Taking much longer to complete normal tasks.
• Misplacing items often.
• Being unable to retrace steps and getting lost.

Conditions That Can Mimic Dementia

Symptoms of some vitamin deficiencies and medical conditions such as vitamin B12 deficiency, infections, hypothyroidism (underactive thyroid), or normal pressure hydrocephalus (a neurological condition caused by the build-up of fluid in the brain) can mimic dementia. Some prescription and over-the-counter medicines can cause dementia-like symptoms. If you have these symptoms, it is important to talk to your health care provider to find out if there are any underlying causes for these symptoms.

How is Dementia Diagnosed?

A healthcare provider can perform tests on attention, memory, problem solving and other cognitive abilities to see if there is cause for concern. A physical exam, blood tests, and brain scans like a CT or MRI can help determine an underlying cause.

What To Do If a Loved One is Showing Symptoms

Talk with your loved one about seeing a health care provider if they are experiencing symptoms of Alzheimer’s dementia to get a brain health check up.

Be Empowered to Discuss Memory Problems

More than half of people with memory loss have not talked to their healthcare provider, but that doesn’t have to be you. Get comfortable with starting a dialogue with your health care provider if you observe any changes in memory, or an increase in confusion, or just if you have any questions. You can also discuss health care planning, management of chronic conditions, and caregiving needs.

What is Alzheimer’s Disease?

• Alzheimer’s disease is the most common type of dementia.
• It is a progressive disease beginning with mild memory loss and possibly leading to loss of the ability to carry on a conversation and respond to the environment.
• Alzheimer’s disease involves parts of the brain that control thought, memory, and language.
• It can seriously affect a person’s ability to carry out daily activities.

Who has Alzheimer’s Disease?

• In 2020, as many as 5.8 million Americans were living with Alzheimer’s disease.
• Younger people may get Alzheimer’s disease, but it is less common.
• The number of people living with the disease doubles every 5 years beyond age 65.
• This number is projected to nearly triple to 14 million people by 2060.
• Symptoms of the disease can first appear after age 60, and the risk increases with age.

What is known about Alzheimer’s Disease?

Scientists do not yet fully understand what causes Alzheimer’s disease. There likely is not a single cause but rather several factors that can affect each person differently.

• Age is the best known risk factor for Alzheimer’s disease.
• Family history—researchers believe that genetics may play a role in developing Alzheimer’s disease. However, genes do not equal destiny. A healthy lifestyle may help reduce your risk of developing Alzheimer’s disease. Two large, long term studies indicate that adequate physical activity, a nutritious diet, limited alcohol consumption, and not smoking may help people. To learn more about the study, you can listen to a short podcast.
• Changes in the brain can begin years before the first symptoms appear.
• Researchers are studying whether education, diet, and environment play a role in developing Alzheimer’s disease.
• There is growing scientific evidence that healthy behaviors, which have been shown to prevent cancer, diabetes, and heart disease, may also reduce risk for subjective cognitive decline. Here’s 8 ways.

What are the warning signs of Alzheimer’s disease?

Alzheimer’s disease is not a normal part of aging. Memory problems are typically one of the first warning signs of Alzheimer’s disease and related dementias.

In addition to memory problems, someone with symptoms of Alzheimer’s disease may experience one or more of the following:

• Memory loss that disrupts daily life, such as getting lost in a familiar place or repeating questions.
• Trouble handling money and paying bills.
• Difficulty completing familiar tasks at home, at work or at leisure.
• Decreased or poor judgment.
• Misplacing things and being unable to retrace steps to find them.
• Changes in mood, personality, or behavior.

Even if you or someone you know has several or even most of these signs, it doesn’t mean it’s Alzheimer’s disease. Know the 10 warning signs (also available in Spanish).

What to do if you suspect Alzheimer’s disease

Getting checked by your healthcare provider can help determine if the symptoms you are experiencing are related to Alzheimer’s disease, or a more treatable conditions such as a vitamin deficiency or a side effect from medication. Early and accurate diagnosis also provides opportunities for you and your family to consider financial planning, develop advance directives, enroll in clinical trials, and anticipate care needs.

How is Alzheimer’s disease treated?

Medical management can improve quality of life for individuals living with Alzheimer’s disease and for their caregivers. There is currently no known cure for Alzheimer’s disease. Treatment addresses several areas:

• Helping people maintain brain health.
• Managing behavioral symptoms.
• Slowing or delaying symptoms of the disease.

Support for family and friends

Currently, many people living with Alzheimer’s disease are cared for at home by family members. Caregiving can have positive aspects for the caregiver as well as the person being cared for. It may bring personal fulfillment to the caregiver, such as satisfaction from helping a family member or friend, and lead to the development of new skills and improved family relationships.

Although most people willingly provide care to their loved ones and friends, caring for a person with Alzheimer’s disease at home can be a difficult task and may become overwhelming at times. Each day brings new challenges as the caregiver copes with changing levels of ability and new patterns of behavior. As the disease gets worse, people living with Alzheimer’s disease often need more intensive care.

You can find more information about caring for yourself and access a helpful care planning form.

What is the burden of Alzheimer’s disease in the United States?

• Alzheimer’s disease is one of the top 10 leading causes of death in the United States.
• The 6th leading cause of death among US adults.
• The 5th leading cause of death among adults aged 65 years or older.

In 2020, an estimated 5.8 million Americans aged 65 years or older had Alzheimer’s disease. This number is projected to nearly triple to 14 million people by 2060.

In 2010, the costs of treating Alzheimer’s disease were projected to fall between $159 and $215 billion. By 2040, these costs are projected to jump to between $379 and more than $500 billion annually.

Death rates for Alzheimer’s disease are increasing, unlike heart disease and cancer death rates that are on the decline. Dementia, including Alzheimer’s disease, has been shown to be under-reported in death certificates and therefore the proportion of older people who die from Alzheimer’s may be considerably higher.

What is known about reducing your risk of Alzheimer’s Disease?

The science on risk reduction is quickly evolving, and major breakthroughs are within reach. For example, there is growing evidence that people who adopt healthy lifestyle habits — like regular exercise and blood pressure management — can lower their risk of dementia. There is growing scientific evidence that healthy behaviors, which have been shown to prevent cancer, diabetes, and heart disease, may also reduce risk for subjective cognitive decline.

If you start to see changes in the way a loved one under 60 acts, speaks, or moves, you may not think of dementia as a cause. Dementia is a loss of thinking, memory, and reasoning that seriously affects your daily activities. It’s more common in older adults. But a group of dementias called frontotemporal disorders, or FTD, occurs most often in people between 45 to 64 years old.

FTD is rare. It sometimes runs in families and can be inherited through certain genes . But in most cases, the cause isn’t known.

The most common symptoms of FTD are changes in behavior and personality. But some people with FTD may instead develop problems with speech and language, called aphasia. FTD can also cause movement problems. (See the Wise Choices box for more symptoms.)

FTD can be challenging to diagnose. “When symptoms arise, it’s very common that other disorders or life circumstances are suspected as the cause,” says Boeve. Causes can include substance use or certain mental health disorders, like depression or psychosis.

“Symptoms may also tend to ebb and flow at first,” says Boeve. “Someone may act very odd, and then things are kind of normal for weeks or months.” But symptoms get worse and become more consistent over time.

Blood tests or imaging tests like MRI or PET scans can sometimes detect certain signs of FTD. “But some people with mild FTD can have normal findings on many of these tests,” Boeve says. If FTD is suspected, talking with a health care provider who’s experienced with FTD can help with a diagnosis.

People with FTD typically live six to eight years. There’s no cure, but some symptoms can be managed. Certain antidepressant drugs can help some patients with mental health symptoms, like apathy, depressed mood, or irritability. “They can also help curb inappropriate behaviors,” Boeve explains. Speech therapy is used for some types of aphasia. Physical therapy can help with some movement problems.

Boeve’s team and other NIH-funded researchers are working to develop better tests and treatments for FTD. Recently, a study by Boeve and others found that exercise slowed the progression of FTD in people with an inherited form of the condition. “For those who were more physically active, their rate of decline was slower,” he says.

Know the Symptoms of FTD

• Problems planning or thinking through the steps to finish a task.
• Difficulty prioritizing tasks or activities.
• Repeating the same activity or same words over and over.
• Acting impulsively or saying or doing inappropriate things.
• Losing interest in family or previously enjoyed activities.
• Losing the ability to demonstrate sympathy or empathy.
• Changes in the types of food a person wants to eat.
• Trouble speaking or understanding words. Difficulty finding the words to say what one means.
• Problems using hands or arms, despite having normal strength.
• Problems with balance and walking.

Scientists around the world are learning more about changes in the brain that can lead to dementia, including Alzheimer’s disease. There are drugs that may improve the quality of life for people living with dementia, but there is no cure. Research may someday lead to new treatments to prevent or slow dementia. In the meantime, though, evidence suggests that the vascular damage that occurs in the brains of most people with dementia may be preventable. Vascular damage to the brain usually occurs gradually, for example due to the cumulative impact of multiple small or “mini” strokes, that occur unnoticed as we age. High blood pressure is the main culprit. Over time, high blood pressure weakens the brain’s blood vessels, and may bring on processes in your body such as strokes that can cause or worsen dementia. The good news is that we know a lot about what causes high blood pressure, and there are many safe, effective ways to get it under control.

What is Dementia?

Most of us know someone — a friend, a family member — living with dementia. Many people think of it as a single disease with the main symptom being memory loss. However, a number of different diseases can result indementia, and the word itself describes a group of symptoms that negatively affect how the brain works. Symptoms include memory loss, as well as changes in mental abilities such as reasoning and judgment, in a way that can make itdifficult to perform any number of once routine daily activities. Some people with dementia can experience changes in personality while others may become agitated, delusional, or have slowed thinking. Memory loss alone does notmean someone has dementia.

Forms of Dementia

While Alzheimer’s disease is the most common dementia diagnosis, the brain changes traditionally associated with Alzheimer’s disease, beta-amyloid plaques and tau tangles, are rarely the only disease processes in people with dementia. Autopsy studies have shown that most patients who die with dementia have a combination of these Alzheimer’s markers along with brain injury due to vascular disease such as silent strokes. Further, there are several other abnormal proteins that can accumulate in the brains of people with dementia. All of this pathological complexity means that a spectrum of dementia forms exists, depending on which combination of these changes are happening in an individual’s brain. Experts now believe that the processes that give rise to vascular disease in the brain and these several forms of dementia often converge, dramatically increasing the likelihood and severity of dementia more than either condition alone.

The Link Between Stroke and Dementia

Strokes are one type of vascular disease that can cause a host of cognitive disabilities, including effects on memory, speech and language, and everyday problem solving. Individuals who have had a stroke are anywhere between 2 times to 8 times more likely to later develop dementia, depending on the severity and number of strokes experienced. But even without suffering an obvious stroke, individuals at risk for stroke may experience cognitive impairment as their blood vessels deteriorate. These brain changes increase one’s risk of later developing age-related cognitive decline and dementia.

How High Blood Pressure Is Linked to Dementia

The heart and brain are the two hardest working organs in your body. They are so closely linked that the conditions that put one at risk of poor health can affect the other. Here are the important ways they are connected:

The heart supplies blood to all the parts of your body, including the brain.

When blood enters the brain, a complicated network of blood vessels distributes oxygen and nutrients to billions of brain cells. Brain health is linked, in part, to the health of blood vessels that supply the brain.

High blood pressure causes these delicate blood vessels to become scarred, narrowed, and diseased. This can affect the bloodstream’s ability to provide nerve cells with the oxygen and nutrients they need to function and survive.

Over time, damage to the brain’s blood vessels may lead to cognitive impairment and vascular dementia. This damage may begin in middle age, years before people start to have memory and other problems related to dementia.

High blood pressure can also lead to “diffuse white matter disease” and silent strokes, which are linked tolater development of cognitive decline and vascular dementia.

High blood pressure is the most preventable cause of stroke. As many as 30 percent of stroke survivors develop post-stroke dementia. Scientists believe that the same risk factors that lead to stroke can also lead to cognitiveimpairment and vascular dementia.

More Risks to Your Brain's Health

Stroke occurs when blood circulation to the brain fails either because blood flow is blocked or because a blood vessel ruptures and bleeds into surrounding brain tissue. Brain cells can die as a result and theconsequences can be mild to severe depending on the size and location of the stroke.

Transient ischemic attack (TIA), sometimes called a mini-stroke, starts just like a stroke but then resolves leaving no noticeable symptoms or deficits. The occurrence of a TIA is a warning that the person is atrisk for a more serious and debilitating stroke.

Silent strokes (or infarcts) show up as multiple areas of ischemic tissue damage (which occurs when an artery to the brain is blocked) on MRI scans or in brains examined after death. In contrast to strokes thatcause immediate and obvious consequences, silent strokes go unnoticed because they are so small, or because they occur in areas that are not directly responsible for movement, speech, vision, or other critical functions.

Diffuse white matter disease is a change in brain structure that can be seen on MRI scans in the majority of older people, affecting as many as 80 percent of those over age 80. Research has demonstrated anassociation between these white matter lesions and blood pressure levels, with higher blood pressure over time being linked to more extensive areas of white matter damage. Some studies also suggest a link between severe whitematter lesions and diminished performance on tests of cognitive function.

Heart disease is a disorder of the blood vessels of the heart that can lead to a heart attack. A heart attack happens when an artery becomes blocked, preventing oxygen and nutrients from getting to the heart.

Are you more likely to get Alzheimer’s disease? Read about who is at risk and what you can do.

Hispanic and African Americans in the United States will see the largest increases in Alzheimer’s disease and related dementias between 2015 and 2060.Dementia is not a specific disease but rather a general term for the impaired ability to remember, think, or make decisions that interferes with doing everyday activities.

Alzheimer’s disease is the most common type of dementia. Current estimates are that about 5.8 million people in the United States have Alzheimer’s disease and related dementias, including 5.6 million aged 65 and older and about 200,000 under age 65 with younger-onset Alzheimer’s.

By 2060, the number of Alzheimer’s disease cases is predicted to rise to an estimated 14 million people, with minority populations being affected the most.

• Cases among Hispanics will increase seven times over today’s estimates.
• Cases among African Americans will increase four times over today’s estimates.

Health conditions such as heart disease and diabetes may account for these differences, as they are more common in the Hispanic and African American populations. Lower levels of education, higher rates of poverty, and greater exposure to adversity and discrimination may also increase risk of Alzheimer’s disease.

Among all races, women are nearly two times more likely to be affected by Alzheimer’s disease than men. The difference is due primarily to women living longer.

Understanding the disparities in Alzheimer’s disease and related dementias is the first step toward developing prevention strategies and targeting services to those most at risk for developing the disease.

Get Your Doctor and Family Involved

Older adults, especially women, Hispanic, and African Americans who are experiencing symptoms of memory loss should have an assessment performed by their health care provider. Doing this early can help focus efforts on timely care for patients and their caregivers. It also provides the opportunity to rule out other possible reasons for memory loss, such as medication side effects, stress, or vitamin deficiencies.

Adults with Down syndrome are living longer lives with increased well-being. In 2020, life expectancy in the United States was age 60, representing an increase of 35 years when compared to 1983.

As with all adults, advancing age increases the chances a person with Down syndrome will develop Alzheimer’s disease. According to the National Down Syndrome Society, about 30% of people with Down Syndrome who are in their 50s have Alzheimer’s disease. About 50% of people with Down syndrome in their 60s have Alzheimer’s disease.

In observance of Sept. 21 as World Alzheimer’s Day and recognition that people with Down syndrome have an increased risk of developing Alzheimer’s, CDC and its partners are focused on sharing information and resources to help support people with Down syndrome, their families, caregivers, health care providers, and public health professionals. Estimates for the number of people with Down syndrome in the United States have grown from nearly 50,000 in 1950 to 206,366 in 2010. Some estimates put the worldwide population of people with Down syndrome at more than 6 million.

What is Down Syndrome

Down Syndrome occurs when an individual has an extra partial, or whole, copy of chromosome 21. It is not yet known why this syndrome occurs, but Down syndrome has always been part of the human condition. It exists in all regions across the globe and commonly affects learning styles, physical characteristics and health.

What Causes the Increased Risk for Alzheimer's Disease Among People With Down Syndrome?

Scientists think the increased risk of Alzheimer’s disease among people with Down syndrome results from the extra genes present as well as other health issues such as congenital heart defects.

• Chromosome 21 plays a key role in the relationship between Down syndrome and Alzheimer’s disease as it carries a gene that produces one of the key proteins, amyloid protein, involved with changes in the brain associated with Alzheimer’s. The build-up of amyloid protein in the brain disrupts the way brain cells communicate to each other. Amyloid accumulation is seen in almost all adults over 40 with Down syndrome. Despite these brain changes, not everyone with Down syndrome develops Alzheimer’s symptoms.
• People with Down syndrome are extremely likely to experience severe issues related to their heart, which places them at increased risk for early onset dementia. About 50% of people with Down syndrome have a congenital heart defect – a condition rarely seen in the general population.

Additionally, adults with Down syndrome experience “accelerated aging,” meaning that in their 40s and 50s, they experience certain conditions that are more commonly seen in much older adults in the general population. These conditions may include:

• Changes in behavior, such as reduced interest in being sociable, conversing or expressing thoughts; irritability, uncooperativeness or aggression; sadness, fearfulness or anxiety;
• Seizures that begin in adulthood;
• Changes in coordination and walking;
• An increase in care needs such as a person’s safety as they navigate their environment; and
• Full dependency for all personal care (bathing, dressing, toileting).

Age When Diagnosed with Alzheimer's Disease

Many people with Down syndrome are diagnosed with Alzheimer’s disease in their 50s, but it is not uncommon for symptoms to occur in their late 40s. The presence of Alzheimer’s disease in people with Down syndrome can lead to a rapid, progressive decline in brain health. And, like most people diagnosed with Alzheimer’s disease, there are variables as to the onset of symptoms and the progression of the disease. Many family members and caregivers observe that people with Down syndrome appear to “slow down” in their late 40s and 50s.

Caregivers Can Help Health Care Professionals

Most adults with Down syndrome do not self-report concerns about memory. Diagnosing Alzheimer’s disease in a person with Down syndrome can be difficult because of the challenges involved in assessing thinking-skill changes in persons with intellectual disabilities. For this reason, information from a caregiver or close family member can be especially helpful for the health care provider during the diagnostic process. Caregivers, for example, can watch for changes in day-to-day function.

Many people wonder if Alzheimer’s disease runs in their family. Is it in your genes? This question isn’t easy to answer. Researchers have identified several genetic variants that are associated with Alzheimer’s and may increase or decrease a person’s risk of developing the disease. What does that mean? Let’s first learn about the role of genes.

What Are Genes?

Human cells contain the instructions needed for a cell to do its job. These instructions are made up of DNA, which is packed tightly into structures called chromosomes. Each chromosome has thousands of segments called genes.

Genes are passed down from a person’s biological parents. They carry information that defines traits such as eye color and height. Genes also play a role in keeping the body’s cells healthy.

Variations in genes — even small changes to a gene — can affect the likelihood of a person developing a disease such as Alzheimer’s.

Do Genes Cause Diseases?

Permanent changes in one or more specific genes are called genetic variants. Some of these variants are quite common in the human population. While most genetic variants don’t cause diseases, some do. In some cases, a person inherits a genetic variant that will almost certainly lead to that individual developing a disease. Sickle cell anemia, cystic fibrosis, and some cases of early-onset Alzheimer’s are examples of inherited genetic disorders. However, other variants may simply increase, or even decrease, a person’s risk of developing that disease. Identifying genetic variants and their effects can help researchers uncover the most effective ways to treat or prevent diseases in an individual.

Additionally, factors such as exercise, diet, chemicals, or smoking can have positive or negative effects by changing the way certain genes work. In the field of epigenetics, researchers are studying how such factors can alter a cell’s DNA in ways that affect gene activity.

Genetic research is a component of precision medicine, an emerging approach that considers individual variability in genes, environment, and lifestyle. Precision medicine will enable researchers and doctors to predict more accurately which treatment and prevention strategies will work in particular groups of people.

Genes and Alzheimer's Disease

In most cases, Alzheimer’s does not have a single genetic cause. Instead, it can be influenced by multiple genes in combination with lifestyle and environmental factors. Consequently, a person may carry more than one gene or group of genes that can either increase or reduce the risk of Alzheimer’s.

Importantly, people who develop Alzheimer’s do not always have a history of the disease in their families. Still, those who have a parent or sibling diagnosed with the disease have a higher risk of developing Alzheimer’s than those without that association.

Genetic variants that affect Alzheimer's disease risk

Ten years ago, researchers knew of only 10 genes linked with Alzheimer’s. Today, scientists have identified more than 70 genetic regions associated with Alzheimer’s. Understanding which genes play a role — and what role they play — may help identify new methods to prevent, delay, or treat dementia.

One well-known gene that influences Alzheimer’s risk is the apolipoprotein E (APOE) gene. The APOE gene is involved in making a protein that helps carry cholesterol and other types of fat in the bloodstream. Problems in this process are thought to contribute to the development of Alzheimer’s. APOE comes in several forms, called alleles (e.g., ε2, ε3).

• APOE ε2 may provide some protection against the disease. If Alzheimer’s occurs in a person with this allele, it usually develops later in life than it would in someone with the APOE ε4 gene. Roughly 5% to 10% of people have this allele.
• APOE ε3, the most common allele, is believed to have a neutral effect on the disease — neither decreasing nor increasing risk of Alzheimer’s.
• APOE ε4 increases risk for Alzheimer’s and is associated with an earlier age of disease onset in certain populations. About 15% to 25% of people have this allele, and 2% to 5% carry two copies.

Each person inherits two APOE alleles, one from each biological parent, meaning people can have one of six possible combinations: 2/2, 2/3, 2/4, 3/3, 3/4, and 4/4. Having two copies of APOE ε4 is associated with a higher risk of Alzheimer’s than having one copy. While inheriting APOE ε4 increases a person’s risk of Alzheimer’s, some people with an APOE ε4 allele never develop the disease.

Researchers are also finding other rare genetic variants, in addition to APOE ε2, that appear to provide some protection against developing Alzheimer’s.

However, prevalence and risk associated with APOE and other genetic variants may not be the same across all population groups. Research suggests that the degree of risk may be affected by genetic ancestry — the global geographic region from which a person is biologically descended — and differ among people of African, Asian, American Indian, and European descent. More research is needed to better understand how certain genetic variants might affect a person’s or group’s risk for Alzheimer’s and to identify treatment and prevention strategies that will work best for that particular group.

Genetic variants that cause Alzheimer's disease

Of the genetic variants so far associated with Alzheimer’s, three rare single-gene variants are known to cause the disease:

• Amyloid precursor protein (APP) on chromosome 21
• Presenilin 1 (PSEN1) on chromosome 14
• Presenilin 2 (PSEN2) on chromosome 1

A child whose biological parent carries a genetic variant for one of these three genes has a 50/50 chance of inheriting that altered version of the gene. If the variant is inherited, the child has a very strong probability of developing Alzheimer’s before age 65 and sometimes much earlier. When someone develops Alzheimer’s before age 65, it’s known as “early-onset Alzheimer’s” or sometimes “younger-onset Alzheimer’s” or “earlier-onset Alzheimer’s.” Less than 10% of all people with Alzheimer’s develop symptoms this early. Of those who do, 10% to 15% can be attributed to changes in APP, PSEN1, and PSEN2.

Changes in these three genes result in the production of abnormal proteins that are associated with the disease. Each of these mutations contributes to the breakdown of APP, a protein that’s function isn’t completely understood. The breakdown of APP is part of a process that makes harmful forms of sticky amyloid fragments. These fragments cluster to form plaques in the brain, which is a hallmark of Alzheimer’s.

In addition to the three genetic variants that are known to cause Alzheimer’s, people with Down syndrome have an extra copy of chromosome 21, which carries the APP gene, and a higher risk of developing early-onset Alzheimer’s. Estimates suggest that 50% or more of people living with Down syndrome will develop Alzheimer’s with symptoms appearing in their 50s and 60s.

Genetic testing for Alzheimer's disease

Genetic tests are not routinely used in clinical settings to diagnose or predict the risk of developing Alzheimer’s or a related dementia.

In some cases, if a person has symptoms at an early age with a strong family history of Alzheimer’s, a neurologist or other medical specialist may order a genetic test for APP, PSEN1, and PSEN2.

Although APOE testing is also available, the results cannot fully predict who will or won’t develop Alzheimer’s. Rather, this type of testing is used primarily in research settings to identify study participants who may have an increased risk of developing Alzheimer’s. This approach helps scientists look for early brain changes and compare the effectiveness of possible treatments for people with different APOE profiles.

Some people learn their APOE status through consumer genetic testing. These products are available for a fee and provide some information around the results and what they mean. While at-home genetic tests are convenient, people considering them may also benefit from talking with a doctor or genetic counselor to better understand this type of test and their test results.

Alzheimer’s disease is a progressive form of dementia that affects nearly 6.5 million people in the United States. It involves parts of the brain that control thought, memory, and language. It begins with mild memory loss and can lead to losing the ability to carry on a conversation and respond to the environment. Memory problems are one of the first warning signs of Alzheimer’s disease and related dementias, and people with the disease can eventually lose the ability to carry on a conversation and respond to the environment.

Alzheimer’s disease is not a normal part of aging, and scientists are working to understand its causes and develop effective treatments. More evidence is emerging that healthy behaviors can lower the risk for Alzheimer’s.

The Connection Between Lifestyle and Alzheimer’s

Promoting healthy aging and reducing the risk of dementia is a national priority. Goal 6 of the National Plan to Address Alzheimer’s Disease promotes health behaviors such as increasing physical activity, eating a healthy diet, and quitting cigarette smoking and excessive drinking.

A CDC study of eight risk factors for Alzheimer’s disease (high blood pressure, physical inactivity, obesity, diabetes, depression, smoking, hearing loss, and binge drinking) among adults 45 and older found the following:

• Nearly half of adults had high blood pressure or did not meet the aerobic physical activity guideline.
• Adults with subjective cognitive decline—worsening confusion or memory loss in the previous year—were more likely to report at least four risk factors (34.3%) than those without cognitive decline (13.1%).
• 3.9% of adults with no risk factors reported subjective cognitive decline, while 25.0% of those with at least four risk factors reported cognitive decline.
• Several modifiable risk factors were more common among African American, Hispanic, and American Indian or Alaska Native populations than other races and ethnicities.

In addition, a University of Minnesota study attributed 41% of dementia cases to 12 modifiable lifestyle factors. Among the 12 lifestyle factors, obesity, high blood pressure, and lack of exercise contributed the most to risk of dementia. Reducing these modifiable risk factors could reduce dementia prevalence.

How You Can Reduce Your Risk of Alzheimer’s

You can help reduce your risk of Alzheimer’s by making healthy lifestyle choices. Here’s what you can do:

• Prevent and manage high blood pressure. Tens of millions of American adults have high blood pressure, and many do not have it under control.
• Manage blood sugar. Learn how to manage your blood sugar if you have diabetes.
• Maintain a healthy weight. Healthy eating and regular physical activity can help you maintain a healthy weight.
• Be physically active. Physical activity can improve thinking, reduce risk of depression and anxiety, and help you sleep better.
• Quit smoking. Quitting smoking now may help maintain brain health and can reduce your risk of heart disease, cancer, lung disease, and other smoking-related illnesses. Free Quitline: 1-800-QUIT-NOW (1-800-784-8669)
• Avoid excessive drinking. If you drink, do so in moderation.
• Prevent and correct hearing loss. Make sure to talk to a hearing care professional to treat and manage hearing loss.
• Get enough sleep. A third of American adults report that they usually get less sleep than the recommended amount. How much sleep do you need? It depends on your age.

If it seems overwhelming to make all these changes at once, try making them gradually. For example, getting an extra 30 minutes of sleep at night, getting an annual physical exam, or simply taking a walk every day may make a big difference to your cognitive health.

Can eating a specific food or following a particular diet help prevent or delay dementia caused by Alzheimer’s disease? Many studies suggest that what we eat affects the aging brain’s ability to think and remember. These findings have led to research on general eating patterns and whether they might make a difference.

The Mediterranean diet, the related MIND diet, and other healthy eating patterns have been associated with cognitive benefits in studies—though the evidence is not as strong as it is for other interventions like physical activity, blood pressure, and cognitive training. Now researchers are more rigorously testing these diets to see if they can prevent or delay Alzheimer’s disease or age-related cognitive decline.

Diet and Dementia Risk

Changes in the brain can occur years before the first symptoms of Alzheimer's appear. These early brain changes suggest a possible window of opportunity to prevent or delay dementia symptoms. Scientists are looking at many possible ways to do this, including drugs, lifestyle changes, and combinations of these interventions. Unlike other risk factors for Alzheimer’s that we can’t change, such as age and genetics, people can control lifestyle choices such as diet, exercise, and cognitive training.

How could what we eat affect our brains? It’s possible that eating a certain diet affects biological mechanisms, such as oxidative stress and inflammation, that underlie Alzheimer’s. Or perhaps diet works indirectly by affecting other Alzheimer’s risk factors, such as diabetes, obesity, and heart disease. A new avenue of research focuses on the relationship between gut microbes—tiny organisms in the digestive system—and aging-related processes that lead to Alzheimer’s.

The Mediterranean and MIND Diets and Alzheimer’s

One diet that shows some promising evidence is the Mediterranean diet, which emphasizes fruits, vegetables, whole grains, legumes, fish and other seafood, unsaturated fats such as olive oils, and low amounts of red meat, eggs, and sweets. A variation called MIND (Mediterranean–DASH Intervention for Neurodegenerative Delay) incorporates the DASH (Dietary Approaches to Stop Hypertension) diet, which has been shown to lower high blood pressure, a risk factor for Alzheimer’s disease.

Some, but not all, observational studies—those in which individuals are observed or certain outcomes are measured, without treatment—have shown that the Mediterranean diet is associated with a lower risk for dementia. These studies compared cognitively normal people who ate a Mediterranean diet with those who ate a Western-style diet, which contains more red meat, saturated fats, and sugar.

Evidence supporting the MIND diet comes from observational studies of more than 900 dementia-free older adults, which showed that closely following the MIND diet was associated with a reduced risk of Alzheimer’s disease and a slower rate of cognitive decline.

Not all studies have shown a link between eating well and a boost in cognition. Overall, the evidence suggests, but does not prove, that following a Mediterranean or similar diet might help reduce the risk for Alzheimer’s dementia or slow cognitive decline. To find out more, scientists supported by NIA and other organizations are conducting clinical trials—considered the gold standard of medical proof—to shed more light on any cause and effect. (See a list of trials that are recruiting participants at the end of this article.)

Scientists aren’t sure why the Mediterranean diet might help the brain. This primarily plant-based diet has been shown to improve cardiovascular health, which may, in turn, reduce dementia risk. In contrast, the typical Western diet increases cardiovascular disease risk, possibly contributing to faster brain aging.

In addition, this diet might increase specific nutrients that may protect the brain through anti-inflammatory and antioxidant properties. It may also inhibit beta-amyloid deposits, which are found in the brains of people with Alzheimer’s or improve cellular metabolism in ways that protect against the disease.

What Do We Know About Individual Foods?

Many foods—blueberries, leafy greens, and curcumin (found in the spice turmeric), to name a few—have been studied for their potential cognitive benefit. These foods were thought to have anti-inflammatory, antioxidant, or other properties that might help protect the brain. So far, there is no evidence that eating or avoiding a specific food can prevent Alzheimer’s disease or age-related cognitive decline.

But scientists continue to look for clues. One study, based on older adults’ reports of their eating habits, found that eating a daily serving of leafy green vegetables such as spinach and kale was associated with slower age-related cognitive decline, perhaps due to the neuroprotective effects of certain nutrients. Another recent study, in mice, found that consuming a lot of salt increased levels of the protein tau, found in the brains of people with Alzheimer’s, and caused cognitive impairment.

What About Vitamins and Supplements?

Observational studies and clinical trials have looked at many over-the-counter vitamins and dietary supplements, including vitamins B and E and gingko biloba, to prevent Alzheimer’s disease or cognitive decline. The idea is that these dietary add-ons might attack oxidative damage or inflammation, protect nerve cells, or influence other biological processes involved in Alzheimer’s.

Despite early findings of possible benefits for brain health, no vitamin or supplement has been proven to work in people. Overall, evidence is weak as many studies were too small or too short to be conclusive.

Take DHA (docosahexaenoic acid) for example. Studies in mice showed that this omega-3 fatty acid, found in salmon and certain other fish, reduced beta-amyloid plaques, a hallmark of Alzheimer’s. However, clinical trials in humans have had mixed results. In a study of 485 older adults with age-related cognitive decline, those who took DHA daily for 24 weeks showed improved learning and memory, compared to those who took a placebo. Another study of 4,000 older adults—conducted primarily to study eye disease—concluded that taking omega-3 supplements, alone or with other supplements, did not slow cognitive decline.

At this time, no vitamin or supplement is recommended for preventing Alzheimer’s or cognitive decline. Although widely available from drugstores and on the Internet, many of these have not been tested for their effects on thinking. Their safety and effectiveness are largely unknown, and they may interact with other medications. (Note: A deficiency in vitamin B12 or folate may cause memory problems, which are reversible with proper treatment.)

Research Continues to Seek Answers

The idea of Alzheimer’s as a metabolic disease that affects the brain, and Alzheimer’s markers such as glucose metabolism, have led scientists in various directions. Besides the Mediterranean diet and its variations, they are looking at other diets as well as individual foods and nutrients.

For example, the ketogenic diet is a high-fat, low-carbohydrate diet that prompts the production of ketones, chemicals that help brain cells work. Studies show that this diet may affect gut bacteria in distinctive ways in people with and without cognitive impairment, and may help brain cells better use energy, improving their overall function.

Researchers are seeking answers to these questions:

• Which foods are critical to brain health and should be included in diet-based interventions?
• Which groups of people are most likely to benefit from dietary interventions targeting prevention of dementia and cognitive decline?
• Do dietary interventions have a greater effect if begun in midlife?

These clinical trials are recruiting participants to test dietary interventions:

• Enhanced Mediterranean Diet for Alzheimer's Disease Prevention—Cognitively normal adults age 65 and older in Kansas City, KS, are randomly assigned to either a Mediterranean diet or a low-fat diet to gauge the impact on cognitive function, brain volume, and other measures.
• Mediterranean Diet, Weight Loss and Cognition in Obese Older Adults—This Chicago study will test the effects of a Mediterranean diet, with and without caloric restriction, to promote weight loss and improve cognitive function in obese older adults.
• Multicultural Healthy Diet to Reduce Cognitive Decline—This 18-month trial will investigate whether an anti-inflammatory diet tailored to a multicultural population in Bronx, NY, can improve cognitive functioning.
• Brain Energy for Amyloid Transformation in Alzheimer’s Disease—Older adults with MCI in Winston-Salem, NC, are randomly assigned to follow either a modified Mediterranean ketogenic (low-carbohydrate/high-fat) diet or an American Heart Association high-carb/low-fat diet for 16 weeks, with follow-up to assess effects on cognition and Alzheimer’s biomarkers.

Ask yourself the five questions below to help understand your risk factors for developing Alzheimer’s disease.

How old are you?

Age is the biggest known risk factor for Alzheimer’s. Most people with Alzheimer’s develop the disease when they are 65 or older, with less than 10% of cases occurring before then. As a person ages past 65, their risk of Alzheimer’s increases. About one in 13 people age 65 to 84 and one in three people 85 and older are living with Alzheimer’s.

Does Alzheimer's run in your family?

Family history is also an important risk factor. People with a parent or sibling diagnosed with Alzheimer’s have a higher risk of developing the disease than those who don’t have family members with the disease. Families can have many things in common, including their genes, environment, and lifestyle, that all may play a role. For example, lifestyle habits such as diet and exercise, which can be influenced by family, can affect overall health and increase risk for Alzheimer’s. Importantly, not everyone with a history of Alzheimer’s in their family will develop the disease and vice versa — not everyone who develops Alzheimer’s has a family history of the disease.

What's your lifestyle?

There are some risk factors, like age, that you cannot change. However, there may be ways to promote better brain health and reduce your risk of Alzheimer’s by addressing certain lifestyle factors, including:

• Unmanaged chronic health issues, such as high blood pressure or hearing loss
• Physical inactivity
• Unhealthy diet
• Alcohol misuse
• Smoking
• Not getting enough sleep or not sleeping well
• Social isolation
• Lack of mental stimulation

Researchers cannot yet say for certain whether making positive changes in these areas can prevent dementia, but doing so is beneficial to living a healthier lifestyle overall. Learn more about leading a healthy lifestyle that may help address risk factors associated with Alzheimer’s and related dementias.

What medical conditions do you have?

Having certain medical conditions may increase your risk of developing Alzheimer’s. For example, cardiovascular disease, which includes conditions such as heart disease, stroke, and coronary artery disease, affects the heart and blood vessels and has been linked to Alzheimer’s.

Several risk factors associated with developing cardiovascular disease are also associated with Alzheimer’s. For example, studies have shown that managing high blood pressure reduces the risk of mild cognitive impairment and the risk of dementia. Specifically, one large clinical trial showed that lowering systolic blood pressure to below 120 mmHg reduced the risk of mild cognitive impairment, and a review of observational studies showed that managing high blood pressure with medication reduced the risk of dementia compared to people with high blood pressure who didn’t take medication. Learn more about blood pressure and Alzheimer’s and ways to control your blood pressure.

Other risk factors associated with both cardiovascular disease and Alzheimer’s include diabetes, overweight or obesity, and high LDL (“bad”) cholesterol.

In addition, other medical conditions associated with a higher risk of Alzheimer’s include:

• Hearing loss
• Depression
• Mild cognitive impairment
• Concussion or other traumatic brain injury

Getting recommended health screenings and regularly checking in with a health care provider can help you learn about and manage medical conditions. Treat high blood pressure with healthy lifestyle changes and medications if prescribed by your doctor. Protect your ears from loud sounds and use hearing restorative devices, such as hearing aids, if needed. Make healthy food choices and get regular exercise to maintain a healthy weight.

What about biomarkers?

Biomarkers are characteristics we can measure that help show what’s happening inside the body. Scientists have identified several biomarkers associated with Alzheimer’s. While testing for biomarkers can provide some information about a person’s risk, these tests can’t tell for sure whether or not someone will develop the disease. Right now, many of these biomarkers are used mostly in research settings or to help doctors in diagnosing the disease.

Genetic variants are a type of biomarker that have been associated with Alzheimer’s risk. Variants in the apolipoprotein E (APOE) gene are one example. A variant called APOE ε4 has been associated with an increased risk of Alzheimer’s in certain populations, while a variant called APOE ε2 may offer some protection against Alzheimer’s in others.

At-home tests are available for a fee to test for APOE variants. People considering such tests will benefit from talking with a doctor or genetic counselor to better understand the test and what their results may mean. Learn more about Alzheimer’s and genetics.

Other biomarkers for Alzheimer’s include levels of the proteins beta-amyloid and tau. Doctors may use brain scans and cerebrospinal fluid tests that measure these protein levels to help determine whether a person’s cognitive difficulties are caused by Alzheimer’s or not. Blood tests are also now available that can measure levels of beta-amyloid. However, none of these tests are commonly used to indicate someone’s risk outside of a research setting.

Identifying who may or may not develop Alzheimer’s is complex. Researchers continue to investigate biomarkers and other risk factors for the disease. Learn more about biomarkers that help diagnose Alzheimer’s or a related dementia.

The bottom line

Scientists are still learning about what causes Alzheimer’s and what puts some people at higher risk than others. While we know some of the factors that influence a person’s risk, there are probably many other factors that have not yet been identified. Talk with a doctor if you have concerns or questions about your risk of developing the disease. The doctor may suggest changes in memory and thinking to watch out for. They may also recommend steps for staying healthy overall to help maintain cognitive health and reduce the risk of dementia.

A healthy heart and a healthy brain are crucial to health in old age. There are many simple and effective lifestyle changes you can make that will reduce your chance of all types of stroke, heart disease, and likely dementia later in life.

Steps to Manage Your Risks

Getting older can bring many changes, both physically and mentally. Even when you’re healthy, your brain and body start slowing down. Maintaining your cognitive health—the ability to clearly think, learn, and remember—is important for your overall well-being.

Many things influence cognitive health. Your genes, lifestyle, and environment can all impact your thinking skills and ability to perform everyday tasks.

“I like to think about the brain as a computer disk for memory and thinking,” explains Dr. Marie Bernard, an aging expert at NIH. “As you get older it gets fuller and fuller. So, it can get more difficult to retrieve data and add data to it. But you’re still able to learn and grow.”

Aging is bound to bring changes. But there are many things you can do to protect your cognitive health as you age. That includes knowing what puts your well-being at risk.

Staying Aware

“Older adults are often targeted by scam artists,” says Dr. Patricia Boyle, who studies the aging brain at Rush University.

Older adults are also more likely than younger ones to pick up the phone without knowing who’s calling, she explains. “Simply by doing that, you’re opening yourself up to a conversation with someone who may be an unscrupulous person trying to steal from you.”

Common scams targeting older adults include identity theft, risky or fake investments, charity scams, and people posing as relatives in distress to ask for money.

Any adult can fall victim to these sorts of scams. But Boyle and her team recently found that low awareness of tactics used by scam artists may be an early indicator of worsening brain function.

In their study, people with low scam awareness were about twice as likely to later develop Alzheimer’s disease as those with high scam awareness.

People should verify any investment proposal or request for money before acting, Boyle explains. Trusted family members or friends may be able to help with this. “Take the time to look into financial propositions and make sure they are legitimate,” she says.

Reversing Changes

If you experience a sudden change in thinking, memory, or mood, it may be caused by a new medication. Some drugs may not cause cognitive changes when taken on their own but can do so when combined with other medications. Even common supplements or over-the-counter remedies can cause these types of interactions.

Sometimes, if you have more than one doctor, one might not know what the others prescribed. “Older adults really benefit from having a list of all their over-the-counter, herbal, and prescribed medications with them whenever they see a health care professional,” says Bernard.

Certain medications can also have dangerous, or even deadly, effects when combined with alcohol. And alcohol alone poses risks for the older brain. It can take less alcohol to alter judgment, coordination, balance, or sleep patterns in an older adult.

Dangerous drinking habits have been rising among older adults in the U.S. A recent NIH-funded study found that 1 in 10 Americans aged 65 or older binge drinks regularly. That means drinking four or more drinks on the same occasion for women and five or more for men.

Older adults may change their drinking habits to cope with the death of a partner or other loved one, or because they’re lonely. But drinking can also be part of social activities for older adults, explains Dr. Edith Sullivan, an alcohol researcher at Stanford University.

“Older adults might feel that ‘well, I’m old now, it’s OK for me to drink,” Sullivan says. But older brains and bodies are especially vulnerable to the effects of alcohol, she adds.

A recent study by Sullivan and her team used brain imaging to see how alcohol affects the brain. They found that older adults who misused alcohol had greater loss of brain tissue compared with their peers who didn’t drink. This was true even if they started misusing alcohol later in life.

The good news, she explains, is that some problems with thinking or memory caused by medications or alcohol misuse can be reversed. “That’s different from classical dementia, which is a one-way street of decline,” says Sullivan.

Building Brain Power

Managing your health conditions is also important. Controlling your blood pressure, for example, reduces the risk of having a small stroke (bleeding from blood vessels in the brain). Small strokes can cause temporary or permanent cognitive problems.

Feeling a sense of purpose in one’s life also seems to help protect older adults from cognitive decline. A study from Boyle and her colleagues found that people who felt more purpose in life had fewer symptoms from brain changes linked to Alzheimer’s disease.

“The aging brain can accumulate Alzheimer’s changes, but if you’re stimulating your brain and strengthening it like a muscle, you may be better able to tolerate those changes,” she says.

Bernard stresses that getting older can also bring cognitive advantages you might not know about.

“Older adults have greater verbal ability than younger adults. They’re better problem solvers. And accumulated experiences are very helpful,” she says.

“Think about the positive things that come with aging,” Bernard says. “It’s a great time to become engaged in meaningful activities, maintain connections to friends and family, develop new connections, and be physically active. And in turn, all of these things can enhance one’s quality of life and one’s aging.”

Protecting Your Brain Health

Good overall health can help you maintain your brain health. These tips can help you stay active and healthier physically and mentally:

• Choose healthy foods whenever possible
• Drink enough fluid
• Limit your use of alcohol
• Don’t smoke or use tobacco products
• Get enough sleep
• Make physical activity part of your routine
• Keep your mind active with learning, teaching, and volunteering
• Stay connected with loved ones, friends, and your community
• Manage chronic health problems like diabetes, high blood pressure, and high cholesterol

High blood pressure is the most important risk factor for brain blood vessel disease. High blood pressure has been associated with clinically apparent stroke, diffuse white matter disease, and silent stroke on MRI brain images and brain examination at autopsy. These in turn have been linked to cognitive decline and dementia. For many reasons, treating high blood pressure and keeping it under control is good for the brain.

How stroke prevention promotes healthy brain aging

Throughout life, a person’s mental faculties are in a constant state of change. For example, mathematicians reach their maximum mental productivity in their third decade. Most people begin to experience very gradual decline in mental abilities as a normal part of healthy aging. Normal age-related changes in cognition are in part due to the limited capacity of the brain’s nerve cells to regenerate. Indeed, our brains become smaller with age. However, after our seventh or eighth decade, an accelerated loss of mental function may signify onset of dementia or less severe cognitive decline.

Alzheimer’s disease is the most common cause of dementia. Current research is exploring how brain cells age and the biologic changes that underlie Alzheimer’s disease, with the ultimate goal of developing treatments and preventive therapies. Another common diagnosis is vascular dementia, which is caused by widespread damage to the brain’s blood vessels. Vascular dementia usually occurs due to the cumulative impact of multiple strokes, including small infarcts which go unnoticed over time.

About 20 percent of the blood circulating through our bodies enters the brain where a highly intricate network of blood vessels distributes oxygen and nutrients to billions of brain cells. When high blood pressure pounds vulnerable brain blood vessels year after year, those vessels become scarred, narrowed, and diseased with arteriosclerosis. This can cause ischemic stroke damage due to lack of adequate blood flow and also upset the delicate balance between the nerve cells’ need for nutrients and what the bloodstream can supply. The most well-known consequence of uncontrolled high blood pressure is stroke, and for years scientists have known that stroke increases the risk of developing dementia. The good news is that controlling hypertension can prevent stroke. In fact, a 10-point reduction in systolic blood pressure can result in a one-third reduction in stroke risk.

Some scientists believe that the hypertension-related changes in brain blood vessels that contribute to stroke also make people more vulnerable to Alzheimer’s dementia. Decades of scientific study have shown that controlling high blood pressure reduces the likelihood of vascular disease. This research offers promise that we may be able to reduce the risk of cognitive decline and dementia by employing what we already know about preventing stroke.

High blood pressure may increase the risk of cognitive impairment

Numerous epidemiological research studies have documented that high blood pressure, especially in midlife, is associated with accelerated impairment of cognitive activity later in life. Many researchers believe that long-term damage to the blood vessels in the brain compromises the supply of nutrients to the areas that are critical to our ability to think, reason, and make decisions. In addition to structural changes within the vessels, high blood pressure leads to cellular and molecular dysfunction in the brain tissue. The accumulation of these negative effects over time may impair our brain’s ability to carry out everyday tasks. Studies have demonstrated an association between high blood pressure and lower measures of global cognition as well as poorer performance on executive function tests (our ability to plan and make decisions) as well as our brain’s processing speed. This contrasts somewhat with the typical short-term memory problems of Alzheimer’s disease. Since these effects occur due to sustained exposures over time, controlling blood pressure in midlife, years before most people become concerned about age-related cognitive loss, maximizes the potential for protecting brain function later in life.

Brain scans reveal subtle brain damage that is linked to hypertension and impaired cognition

Changes in brain structure can be seen on MRI scans in the majority of older individuals. Scientists have been trying to understand the causes and consequences of these changes in the bundles of fibers that connect brain regions. Called “diffuse white matter disease” the fibers appear on MRI brain scans as coalescing, multiple bright spots in deep structures of the brain. Disease in the small blood vessels that supply the center of the brain contributes to these changes. These abnormalities are prevalent in senior populations, affecting as many as 80 percent of those over age 80, but their number, size, severity, and rate of progression vary. Research has demonstrated an association between these white matter lesions and blood pressure levels, with higher blood pressure levels over time being linked to more extensive areas of white matter damage. Some studies also suggest a link between severe white matter lesions and enhanced risk of diminished cognitive function or dementia.

“Silent” strokes linked to high blood pressure

Another type of subtle brain damage is the “silent” stroke. Silent strokes (or infarcts) show up as multiple areas of ischemic tissue damage on MRI scans or in brains examined after death. In contrast to strokes that cause immediately obvious consequences, silent infarcts go unnoticed because they are so small, or because they occur in areas that are not directly responsible for movement, speech, vision, or other critical functions. These silent infarcts increase in prevalence as we age, affecting as many as 30 percent of older individuals. Like white matter lesions, silent infarcts can vary in size, quantity, and location. A strong body of evidence links these silent infarcts to high blood pressure and suggests that they contribute to cognitive impairment and dementia. In addition, microscopic strokes, which are not visible on MRI scans but can be detected with microscopic brain tissue examination during autopsy, are even more prevalent and have been linked to poorer cognitive function and dementia.

High blood pressure may increase the risk for dementia

Dementia is a clinically diagnosed condition characterized by significant, sustained decline of overall mental abilities that is severe enough to interfere with normal daily activities. The most commonly diagnosed dementia is Alzheimer’s disease, another very common diagnosis is vascular dementia. Epidemiologic studies have documented an association between high blood pressure and other cardiovascular risk factors in midlife with the onset of dementia at later ages. Data from randomized controlled trials of different blood pressure medications seem to suggest that controlling blood pressure limits cognitive decline and dementia, but it is difficult to design studies that address the question in a definitive way. For decades, research has shown that dementia risk strikingly increases in the years after a stroke, but exactly why remains a mystery. Moreover, population-based autopsy studies have shown that most patients who die with dementia often have a combination of both Alzheimer’s pathology and brain injury due to vascular disease or silent strokes, so-called “mixed dementia.” Experts now believe that the processes that give rise to vascular disease in the brain and Alzheimer’s disease may converge, dramatically increasing the likelihood and severity of dementia more than either condition alone. Ongoing research is exploring the biological mechanisms that underlie the relationship between high blood pressure and other cardiovascular risk factors and development of dementia.

Turning the tide?

Over the past five decades, stroke rates in the United States have decreased by 70 percent as blood pressure control has become the standard of care. If there is a link between vascular diseases, including stroke, and dementia, then it would be expected that dementia rates should exhibit a parallel decrease. In fact, recently a number of studies have reported decreased dementia incidence rates in the U.S. and other developed countries.

As they get older, many people worry about developing Alzheimer's disease or a related dementia. If they have a family member with Alzheimer's, they may wonder about their family history and genetic risk. As many as 5.5 million Americans age 65 and older live with Alzheimer's. Many more are expected to develop the disease as the population ages—unless ways to prevent or delay it are found.

Although scientists have conducted many studies, and more are ongoing, so far nothing has been proven to prevent or delay dementia caused by Alzheimer's disease. But researchers have identified promising strategies and are learning more about what might—and might not—work.

We know that changes in the brain can occur many years before the first symptoms of Alzheimer's appear. These early brain changes point to a possible window of opportunity to prevent or delay debilitating memory loss and other symptoms of dementia. While research may identify specific interventions that will prevent or delay the disease in some people, it's likely that many individuals may need a combination of treatments based on their own risk factors.

Researchers are studying many approaches to prevent or delay Alzheimer's. Some focus on drugs, some on lifestyle or other changes. Let's look at the most promising interventions to date and what we know about them.

Can Increasing Physical Activity Prevent Alzheimer's Disease?

Physical activity has many health benefits, such as reducing falls, maintaining mobility and independence, and reducing the risk of chronic conditions like depression, diabetes, and high blood pressure. Based on research to date, there's not enough evidence to recommend exercise as a way to prevent Alzheimer's dementia or mild cognitive impairment (MCI), a condition of mild memory problems that often leads to Alzheimer's dementia.

Years of animal and human observational studies suggest the possible benefits of exercise for the brain. Some studies have shown that people who exercise have a lower risk of cognitive decline than those who don't. Exercise has also been associated with fewer Alzheimer's plaques and tangles in the brain and better performance on certain cognitive tests.

While clinical trials suggest that exercise may help delay or slow age-related cognitive decline, there is not enough evidence to conclude that it can prevent or slow MCI or Alzheimer's dementia. One study compared high-intensity aerobic exercise, such as walking or running on a treadmill, to low-intensity stretching and balance exercises in 65 volunteers with MCI and prediabetes. After 6 months, researchers found that the aerobic group had better executive function—the ability to plan and organize—than the stretching/balance group, but not better short-term memory.

Several other clinical trials are testing aerobic and nonaerobic exercise to see if they may help prevent or delay Alzheimer's dementia. Many questions remain to be answered: Can exercise or physical activity prevent age-related cognitive decline, MCI, or Alzheimer's dementia? If so, what types of physical activity are most beneficial? How much and how often should a person exercise? How does exercise affect the brains of people with no or mild symptoms?

Can Controlling High Blood Pressure Prevent Alzheimer's Disease?

Controlling high blood pressure is known to reduce a person's risk for heart disease and stroke. The NASEM committee of experts concluded that managing blood pressure when it's high, particularly for middle-aged adults, also might help prevent or delay Alzheimer's dementia.

Many types of studies show a connection between high blood pressure, cerebrovascular disease (a disease of the blood vessels supplying the brain), and dementia. For example, it's common for people with Alzheimer's-related changes in the brain to also have signs of vascular damage in the brain, autopsy studies show. In addition, observational studies have found that high blood pressure in middle age, along with other cerebrovascular risk factors such as diabetes and smoking, increase the risk of developing dementia.

Clinical trials—the gold standard of medical proof—are underway to determine whether managing high blood pressure in individuals with hypertension can prevent Alzheimer's dementia or cognitive decline.

One large clinical trial—called SPRINT-MIND (Systolic Blood Pressure Intervention Trial–Memory and Cognition in Decreased Hypertension)—found that lowering systolic blood pressure (the top number) to less than 120 mmHg, compared to a target of less than 140 mmHg, did not significantly reduce the risk of dementia. Participants were adults age 50 and older who were at high risk of cardiovascular disease but had no history of stroke or diabetes.

However, the multiyear study did show that this intensive blood pressure lowering significantly reduced the risk of MCI, a common precursor of Alzheimer’s, in the participants. In addition, researchers found that it was safe for the brain.

The results of SPRINT-MIND provide further evidence of the connection between cardiovascular health and brain health. Further studies are needed to determine which people, at what age, might benefit most from particular blood pressure management approaches, and how these approaches affect the risk of dementia, including Alzheimer’s disease.

While research continues, experts recommend that people control high blood pressure to lower their risk of serious health problems, including heart disease and stroke.

Can Cognitive Training Prevent Alzheimer's?

Cognitive training involves structured activities designed to enhance memory, reasoning, and speed of processing. There is encouraging but inconclusive evidence that a specific, computer-based cognitive training may help delay or slow age-related cognitive decline. However, there is no evidence that it can prevent or delay Alzheimer's-related cognitive impairment.

Studies show that cognitive training can improve the type of cognition a person is trained in. For example, older adults who received 10 hours of practice designed to enhance their speed and accuracy in responding to pictures presented briefly on a computer screen ("speed of processing" training) got faster and better at this specific task and other tasks in which enhanced speed of processing is important. Similarly, older adults who received several hours of instruction on effective memory strategies showed improved memory when using those strategies. The important question is whether such training has long-term benefits or translates into improved performance on daily activities like driving and remembering to take medicine.

Some of the strongest evidence that this might be the case comes from the NIA-sponsored Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE) trial. In this trial, healthy adults age 65 and older participated in 10 sessions of memory, reasoning, or speed-of-processing training with certified trainers during 5 to 6 weeks, with "booster sessions" made available to some participants 11 months and 3 years after initial training. The sessions improved participants' mental skills in the area in which they were trained (but not in other areas), and improvements persisted years after the training was completed. In addition, participants in all three groups reported that they could perform daily activities with greater independence as many as 10 years later, although there was no objective data to support this.

Findings from long-term observational studies—in which researchers observed behavior but did not influence or change it—also suggest that informal cognitively stimulating activities, such as reading or playing games, may lower risk of Alzheimer's-related cognitive impairment and dementia. For example, a study of nearly 2,000 cognitively normal adults 70 and older found that participating in games, crafts, computer use, and social activities for about 4 years was associated with a lower risk of MCI.

Scientists think that some of these activities may protect the brain by establishing "reserve," the brain's ability to operate effectively even when it is damaged or some brain function is disrupted. Another theory is that such activities may help the brain become more adaptable in some mental functions so it can compensate for declines in others. Scientists do not know if particular types of cognitive training—or elements of the training such as instruction or social interaction—work better than others, but many studies are ongoing.

Can Eating Certain Foods Prevent Alzheimer's Disease?

People often wonder if a certain diet or specific foods can help prevent Alzheimer's disease. The recent NASEM review of research did not find enough evidence to recommend a certain diet to prevent cognitive decline or Alzheimer's. Despite observational studies that link Mediterranean-style diets to brain health, clinical trials have not shown strong evidence. Many trials have focused on individual foods rather than comprehensive diets. Newer studies of diets, such as the MIND diet—a combination of the Mediterranean and DASH (Dietary Approaches to Stop Hypertension) diets—are underway. In general, a healthy diet is an important part of healthy aging.

Targets of Alzheimer's Disease Prevention Research

Researchers are exploring these and other interventions that may help prevent, delay, or slow Alzheimer's dementia or age-related cognitive decline. Other research targets include:

• New drugs to delay onset or slow disease progression
• Diabetes treatment
• Depression treatment
• Blood pressure- and lipid-lowering treatments
• Sleep interventions
• Social engagement
• Vitamins such as B12 plus folic acid supplements and D
• Combined physical and mental exercises

Be Cautious About Alzheimer's "Cures"

Because Alzheimer's disease is so devastating, some people are tempted by untried or unproven "cures." Check with your doctor before trying pills or any other treatment or supplement that promises to prevent Alzheimer's. These "treatments" might be unsafe, a waste of money, or both. They might even interfere with other medical treatments that have been prescribed.

What's the Bottom Line on Alzheimer's Prevention?

Alzheimer's disease is complex, and the best strategy to prevent or delay it may turn out to be a combination of measures. In the meantime, you can do many things that may keep your brain healthy and your body fit.

Older African Americans with mild cognitive impairment (MCI) who got help setting goals to be more socially, physically, or cognitively active had slower memory decline than those who did not receive such help, concludes an NIA-funded study published Sept. 10 in JAMA Neurology. The results point to a possible way to reduce dementia risk in African Americans, who are more likely than whites to develop the condition.

Past studies suggest that a more active lifestyle may help prevent cognitive decline, but few of these studies have included African Americans. MCI—a condition in which people have more memory problems than normal for their age—often, but not always, leads to memory loss and other signs of dementia.

In the study by researchers at Thomas Jefferson University, Philadelphia, 221 African Americans age 65 and older with MCI (average age, 76 years; 79 percent female) were randomly assigned to one of two interventions, and 164 completed the trial. One group received “behavioral activation,” in which community health workers helped them choose goals to be more active, then develop step-by-step action plans. Goals included, for example, relearning how to play chess or rejoining a church group. The control group received “supportive therapy,” conversations with community health workers that did not involve setting goals. Both groups had 11 one-on-one, in-home sessions with African-American community health workers, with each session lasting 1 hour, over 2 years.

After 2 years, the behavioral-activation group participated in significantly more cognitive activities, the researchers found. There were no differences in physical or social activity levels. Both groups had memory decline, measured by performance on a standard memory test, but the behavioral-activation group declined by just 1.2 percent, compared with 9.3 percent for the control group. In addition, behavioral activation was associated with stable everyday function and improved executive function.

The study provides evidence that a behavioral intervention can slow memory decline in older African Americans at risk for dementia. Although several factors may influence cognitive decline in this population, it’s possible that planning a more active lifestyle could reduce the disparity in dementia risk between African Americans and whites.