Is Alzheimer’s Hereditary?

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Yes, Alzheimer’s disease can be hereditary, especially in cases of early-onset Alzheimer’s, which develops before the age of 65. But the vast majority of cases aren’t inherited, and doctors still don’t know exactly what causes brain cells to be damaged and destroyed. Here’s what we do know about the role genes play in determining if you could develop Alzheimer’s.

The genetics of Alzheimer’s

Scientists break down the genetic components of Alzheimer’s into two main categories: risk genes and determinant genes. It’s important to understand how each one may (or may not) affect your risk of developing the disease.

Risk genes

Certain genes can affect the likelihood that someone will develop Alzheimer’s. The apolipoprotein E (APOE) gene, found on chromosome 19, is the most common gene linked to late-onset Alzheimer’s. Everyone inherits APOE genes from their parents, one from your mother and one from your father. But those who inherit a version of this gene known as APOE-e4 are more likely to develop Alzheimer’s than those who don’t. Risk rises if you inherit APOE-e4 from both parents.

But here’s an important piece to understand: Risk genes are not all or nothing. Some people with APOE-e4 may develop the disease, while others with the same genes will not. And many people who don’t have APOE-e4 will also develop Alzheimer’s. Researchers have been able to pinpoint a link between the genes and the disease, but not causation.

Deterministic genes

There are certain genes that have been directly linked to Alzheimer’s. These genes, found on chromosomes 21, 14, and 1, are responsible for the formation of three different proteins—amyloid precursor protein (APP), presenilin-1 (PS-1), and presenilin-2 (PS-2), respectively. People who carry mutations in any of these genes produce abnormal forms of the corresponding proteins, leading to the formation of amyloid plaques, the distinctive protein clumps found in the brains of people with Alzheimer’s.

These gene mutations are linked to early-onset Alzheimer’s. People who inherit one of these gene mutations from either parent are very likely to develop Alzheimer’s symptoms before the age of 65.

But here’s an important piece to understand: These genetic changes are still very rare and only a small slice of people with Alzheimer’s (1 to 5 percent of total cases) have deterministic genes that cause the disease. Until more research is done, it’s still too hard to pinpoint genetic links in most cases of Alzheimer’s.

Should you consider genetic testing?

Not so fast. Right now, experts do not recommend that most people be tested for APOE-e4, since it’s hard to pinpoint exactly how it affects risk. Talking with a doctor and a genetic counselor will help determine if it makes sense for you to be tested for the mutations linked to early-onset Alzheimer’s.

Finding out if you have these genes may only lead to more stress and anxiety because doctors can’t predict who will develop the condition and who won’t—and remember: There’s still no cure for Alzheimer’s.

Plus, many doctors believe that a majority of people who develop the disease get it because of a combination of factors that may include genetics, but also includes environmental and lifestyle factors. You may be better off focusing on what you can control: taking care of yourself through diet and exercise to limit the risk of chronic conditions that may affect the brain, like heart disease, high blood pressure, and diabetes.

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