by National Institute on Aging

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.

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.

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.

Hospitalization due to infection may increase a person’s likelihood of developing dementia, according to a large NIA-funded observational study. The researchers found people hospitalized with an infection were more likely to be diagnosed with dementia years later than those who were not hospitalized with infections. The results, published in JAMA Network Open, suggest measures taken to prevent infection may also contribute to dementia prevention.

Previous findings have suggested an association between dementia and certain types of infections, such as systemic and central nervous system infections. Additionally, hospitalization for any reason, but notably for infection and critical illness, has been linked to cognitive decline. Building on these findings, a team led by researchers at the University of Minnesota and an NIA scientist explored the association between hospitalization for infection and dementia by looking at data from the Atherosclerosis Risk in Communities (ARIC) study, an observational study that has followed participants for up to 32 years.

Using data from 15,688 participants who did not have dementia when they entered the ARIC study, the scientists determined whether participants were hospitalized for an infection, and how many subsequently developed dementia three to 20 years later. The research team also investigated whether different types of infections were associated with varying dementia risk.

During the maximum follow-up period of 32 years, 19% of participants were diagnosed with dementia, and 38% were hospitalized with an infection. The researchers determined people who were hospitalized with an infection were 70% more likely to be diagnosed with dementia than those who were not. The types of infections most associated with dementia were blood and circulatory, urinary, and hospital-acquired infections, such as catheter-associated urinary tract infections.

The study’s findings provide evidence that hospitalization with an infection increases one’s risk of developing dementia, underscoring the importance of infection prevention when and if possible. More research on the links between infection and cognition could also lead to improved dementia screening practices.

This research was supported in part by NIA grants K76AG057020 and RF1AG072387 and the Intramural Research Program at NIA (ZIAAG000348).

Preventing or controlling high blood pressure, not only helps your heart, but may help your brain too. Decades of observational studies have shown that having high blood pressure in midlife — the 40s to early 60s — increases the risk of cognitive decline later in life. In addition, the Sprint-Mind study, a nationwide clinical trial, showed that intensive lowering of blood pressure (even below the previous standard target of 140 for systolic blood pressure) lowers the risk for mild cognitive impairment, which is a risk factor for dementia.

High blood pressure often does not cause signs of illness that you can see or feel. Routine visits to your doctor will help pick up changes in your blood pressure, even though you might feel fine. To control or lower high blood pressure, your doctor may suggest exercise, changes in your diet, and if needed — medications. These steps can help protect your brain and your heart.

A healthy diet can help reduce the risk of many chronic diseases such as heart disease or diabetes. It may also help keep your brain healthy.

In general, a healthy diet consists of fruits and vegetables; whole grains; lean meats, fish, and poultry; and low-fat or nonfat dairy products. You should also limit solid fats, sugar, and salt. Be sure to control portion sizes and drink enough water and other fluids.

Researchers are looking at whether a healthy diet can help preserve cognitive function or reduce the risk of Alzheimer’s. For example, there is some evidence that people who eat a Mediterranean diet have a lower risk of developing dementia.

While scientists aren’t sure yet why the Mediterranean diet might help the brain, its effect on improving cardiovascular health might in turn reduce dementia risk. In contrast, the typical Western diet often increases cardiovascular disease risk, possibly contributing to faster brain aging.

Researchers have developed and are testing another diet, called MIND, a combination of the Mediterranean and DASH (Dietary Approaches to Stop Hypertension) diets. According to observational studies of more than 900 dementia-free older adults, closely following the MIND diet was associated with a reduced risk of Alzheimer’s and a slower rate of cognitive decline.

Learn more about diet and prevention of Alzheimer’s disease.

Be Physically Active

Being physically active — through regular exercise, household chores, or other activities — has many benefits. It can help you:

Keep and improve your strength

Have more energy

Improve your balance

Prevent or delay heart disease, diabetes, and other concerns

Studies link ongoing physical activity with benefits for the brain and cognition as well, although a strong link between physical activity and Alzheimer’s disease prevention has not yet been documented.

In one study, exercise stimulated the human brain’s ability to maintain old network connections and make new ones that are vital to cognitive health. Other studies have shown that exercise increases the size of a brain structure important to memory and learning, resulting in better spatial memory. Aerobic exercise, such as brisk walking, is thought to be more beneficial to cognitive health than nonaerobic stretching and toning exercise. One study found that the more time spent doing a moderate levels of physical activity, the greater the increase in brain glucose metabolism — or how quickly the brain turns glucose into fuel — which may reduce the risk for developing Alzheimer’s disease.

Federal guidelines recommend that all adults get at least 150 minutes (2.5 hours) of physical activity each week. Walking is a good start. You can also join programs that teach you to move safely and prevent falls, which can lead to brain and other injuries. Check with your health care provider if you haven’t been active and want to start a vigorous exercise program.