Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community


    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Alzheimer's Disease Health Center

Select An Article
Font Size

Who Gets Alzheimer's? Genes Hold Key

But Genes Aren't Destiny, Study of Identical Twins Shows
WebMD Health News
Reviewed by Louise Chang, MD

Will you ever get Alzheimer's disease? Genetics may have the answer. The genes you've inherited carry most of the risk, an identical-twin study shows.

It's surprising news. While people clearly inherit Alzheimer's disease risk, most researchers have given equal blame to "environmental factors." These factors may include things we encounter, things we do or don't do, or diseases we develop.

But an international study of nearly 12,000 Swedish twin pairs -- a fourth of them identical twins -- now finds that some 80% of Alzheimer's risk is genetic. University of Southern California psychologist Margaret Gatz, PhD, and colleagues report the findings in the February issue of Archives of General Psychiatry.

"It appears that genetic influences outweigh environmental influences in relative importance for Alzheimer's risk," Gatz tells WebMD.

What this means is that close relatives of people with Alzheimer's disease are at much higher risk of getting the disease than people without such a relative. What it does not mean is that if you have such a relative, you're doomed to get Alzheimer's.

"'Genetic' does not mean cast in stone," Gatz tells WebMD. "In no way is having a relative with Alzheimer's disease -- even a genetically identical twin -- a guarantee that a person is going to get Alzheimer's disease."

When 1 Twin Has Alzheimer's

Gatz's team screened for dementia among twins over age 65 in the Swedish Twin Registry. They then tested each twin with dementia for Alzheimer's disease. Extensive medical and lifestyle information was available for each study participant.

The researchers found that genetic inheritance explained about 80% of Alzheimer's risk. Environmental factors not shared among twins explained the other 20%, as might be expected.

But even among identical twins -- who share the same genetic makeup -- Alzheimer's disease in one twin did not mean the other twin inevitably got the disease.

Among male identical twins, when one brother had Alzheimer's disease, the other developed the disease 45% of the time.

Among female identical twins, when one sister had Alzheimer's disease, the other developed the disease 60% of the time.

The difference between men and women, Gatz says, is simply that women live longer and thus have a better chance of surviving long enough to get Alzheimer's disease.

Next Article:

Today on WebMD

Remember your finger
When it’s more than just forgetfulness.
senior man with serious expression
Which kinds are treatable?
senior man
Common symptoms to look for.
mri scan of human brain
Can drinking red wine reverse the disease?
eating blueberries
Colored mri of brain
Close up of elderly couple holding hands
mature woman
Woman comforting ailing mother
Senior woman with serious expression