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What causes Alzheimer's disease?

A female doctor is pointing to a brain scan while an older man looks at the scan.

Discover some of the factors that may influence whether someone gets this brain disease.

It's among the deepest mysteries surrounding Alzheimer's disease: Why do some people get the disease while others don't?

No one knows exactly the answer to that question in every case. But scientists do know that the disease is related to certain changes in the brain. And we know that some factors put a person at risk for developing Alzheimer's disease.

For example:

Plaques and tangles. People with Alzheimer's tend to have many abnormal clumps and strands of protein—also known as amyloid plaques and neurofibrillary, or tau, tangles—in and around the nerve cells in their brains.

In 1906, German physician Alois Alzheimer (for whom Alzheimer's disease is named) noticed these formations in the brain of a woman who died of what was thought to be an unusual mental illness, according to the National Institute on Aging (NIA).

Many years later, scientists are still learning about the role of plaques and tangles in Alzheimer's. But they seem to be related to the disruption and death of the brain's nerve cells, which takes place over many years.

Age. Getting older is the biggest risk factor for Alzheimer's disease. In fact, the likelihood of developing Alzheimer's doubles every five years after age 65, the Alzheimer's Association reports.

However, some younger people have been diagnosed with Alzheimer's. When the disease occurs before age 65, it is often referred to as early onset Alzheimer's.

Despite the strong connection to aging, Alzheimer's disease should not be seen as a normal result of getting older. Maintaining a healthy brain as we get older is a realistic and worthwhile goal.

Family history and genetics. Having a family history of Alzheimer's can increase your risk for it too. The risk goes up the more family members you have with Alzheimer's.

Alzheimer's may run in some families because of genetics. Scientists have identified a gene that increases a person's risk for the disease, and it's linked to early onset Alzheimer's, the NIA notes.

Or there might be something in a family's shared environment that raises their Alzheimer's risk.

One environmental factor that does not appear to cause Alzheimer's? Aluminum exposure—such as from cooking pots and drinking cans, according to experts.

Keep in mind: It's not currently possible to predict who will and won't get Alzheimer's based on family history alone. In other words, just because a parent, brother or sister has Alzheimer's, that doesn't mean you'll get it too.

Vascular and metabolic diseases. Having a condition that damages your heart and blood vessels may increase the risk for Alzheimer's and a related condition called vascular dementia. These risk-increasing conditions include heart disease, diabetes, stroke, high blood pressure and high cholesterol.

All of these conditions damage the arteries, reducing the supply of oxygen to the brain and possibly disrupting connections between nerve cells.

Race or ethnicity. More older Latinos and African Americans get Alzheimer's than do older white adults. This may be because these groups have higher rates of vascular diseases, though researchers aren't sure, the Alzheimer's Association reports.

Is there anything you can do to help reduce your risk?

Some Alzheimer's risk factors—like getting older—are beyond your control. But there are some lifestyle changes that may help keep your brain healthy and possibly even lower your risk for Alzheimer's as you age.

According to the NIA and the Alzheimer's Association, here are some things you can do:

  • Work with your doctor to manage any heart or blood vessel diseases you have.
  • Eat a healthy diet rich in plant-based foods.
  • Stay socially active, and keep your brain busy with hobbies or other mentally stimulating activities.
  • Don't smoke.
  • Watch your alcohol intake.
  • Exercise regularly.

Research continues

There probably isn't just one factor that leads to the disease. Instead, a combination of risks may work together to cause Alzheimer's. These factors may affect each person differently.

For more information, visit alz.org.

Reviewed 9/13/2021

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