Why Do People Get Dementia? Here’s What We Know

If you walk through a retirement community and spend a day talking to different residents of similar ages, you’ll find each person’s brain health is unique. Some residents may show signs of dementia, like trouble remembering and reasoning, while others seem mentally sharp. But why? The short answer is that no one knows for sure.

The most common cause of dementia in older people is Alzheimer’s disease. Dementia can also develop due to other conditions, like brain damage from a stroke, injury, or infection. But Alzheimer’s disease is unique among dementia causes because we can’t say for sure why it happens.

When someone develops dementia after a stroke or head injury, doctors can link the dementia to a clear cause. However, this isn’t true for Alzheimer’s disease — and since we can’t link the disease to exact causes, we can’t predict who will get Alzheimer’s or figure out how to stop it before it starts.

But even though we don’t completely understand why some people develop Alzheimer’s disease, scientists have been working hard for decades to find the answers. Thanks to their work, we do have some clues about the factors that raise our risk of developing Alzheimer’s disease and dementia.

Age Is the Top Alzheimer’s Risk Factor

Most people associate Alzheimer’s disease and dementia with older people, and there’s a good reason for that: advanced age is the condition’s biggest known risk factor. Most individuals who have Alzheimer’s disease are 65 and older, and the risk for the disease doubles every five years after age 65. At age 85, almost one-third of people have Alzheimer’s.

But it’s clear that age isn’t the only factor, since some people live into their 80s, 90s, and even 100s without showing any signs of Alzheimer’s disease or dementia.

A Family History of Alzheimer’s Increases Your Chances of Developing the Disease

If you have a family member with Alzheimer’s disease, especially a close family member like a parent or sibling, then you’re more likely than the average person to develop Alzheimer’s yourself. The more family members you have with Alzheimer’s disease, the higher your risk is.

When a disease tends to run in families like Alzheimer’s does, it usually means the disease develops because of our genes, our environment, or both. In the case of Alzheimer’s, scientists know our genes play a role in determining whether we develop the disease, and they believe environmental factors may affect our risk too.

There’s a Connection Between Heart Health and Dementia

Lots of evidence shows that heart health and brain health are related. This makes sense because our brains need blood, which pumps out of our hearts, to keep functioning. Conditions that can damage your heart, like coronary artery disease, diabetes, and high blood pressure, can also raise your risk of developing Alzheimer’s disease.

Head Injuries Are Also Linked to Alzheimer’s

People who suffer repeated head injuries, including concussions, seem to experience higher rates of Alzheimer’s disease as they get older. However, our understanding of this connection is still at a very early stage, and scientists agree we need to do much more research in this area.

Your Ethnic Background May Play a Role

Research has shown that people of Latino and African American descent develop Alzheimer’s disease at higher rates than people of other ethnic backgrounds. For Latinos, their risk is about one-and-a-half times that of people who identify as white, and for African Americans, their risk is about two times that of white people.

Right now, scientists aren’t certain why this increased risk exists for people of Latino and African American descent. However, scientists know that both of these ethnic groups experience higher rates of heart disease and blood vessel disease compared to people who identify as white. Since we already know heart health and Alzheimer’s risk are related, this may help explain why Latinos and African Americans develop Alzheimer’s more often.

A Healthy Lifestyle May Decrease Your Risk of Alzheimer’s

Scientists believe our overall health affects our brain health and our risk for Alzheimer’s disease. Of course, there’s always plenty of debate about what “health” and “healthy living” look like. Some of the healthy behaviors that scientists and health experts feel most confident about recommending include:

  • Eating a heart-healthy diet that includes lots of vegetables, fruits, and whole grains
  • Staying socially active
  • Avoiding tobacco use and excessive alcohol consumption
  • Getting regular physical exercise
  • Performing activities that keep your brain engaged (like reading, puzzles, and games)

We’re Working to Uncover the Causes of Alzheimer’s and You Can Help!

Even though we’ve learned a lot in recent decades about the factors that affect our risk for Alzheimer’s disease, our current understanding is like a giant jigsaw puzzle with only the borders in place. We still have so much to learn, and putting together all those missing pieces will take a lot of time, resources, and hard work.

Right now, Boston University School of Public Health and Savonix are conducting a study that will help us learn more about the factors that affect brain health as we age, and you can help. The study is called the ASSIST Study, and researchers have never attempted a brain health study like it before.

The goal for the three-year study is to gather data from at least 400,000 individuals, with an emphasis on diversity. By examining a larger and more diverse population than any study before it, the ASSIST Study will identify how a wide range of factors influence our risk of developing dementia.

Even if you don’t have much available time, the ASSIST Study isn’t like other medical studies. You can participate in just 45 minutes from the comfort of your home. All you need to do is visit assiststudy.org and select the “Join the Study” button.

The ASSIST Study is open to all United States residents ages 22 and older. Your health status doesn’t matter, so both you and the person you’re caring for can participate and provide valuable data. You only need to meet one other requirement to participate:

  • You must have an Apple iPhone® 5s or later with iOS version 11.0 or later, and you must use the Health app to track your health information


  • You must have an Apple iPad® with iOS version 11.0 or later or an Android™ device, such as a tablet or phone, running version 6 or later


RELATED: Can Data Unlock the Cure for Alzheimer’s Disease?

Ready to Join the Study?

You can join the fight against Alzheimer’s disease and dementia right now. To get started, go to www.assiststudy.org and select the button that says, “Join the Study.” Follow the instructions and do your part today!


Causes and risk factors. (n.d.). Alzheimer’s Association. Retrieved from https://www.alz.org/alzheimers-dementia/what-is-alzheimers/causes-and-risk-factors

Dementia. (n.d.). Mayo Clinic. Retrieved from https://www.mayoclinic.org/diseases-conditions/dementia/symptoms-causes/syc-20352013

Ellison, J.M. (2017, October 4). BrightFocus Foundation. Retrieved from https://www.brightfocus.org/alzheimers/article/what-causes-dementia