What Does It Mean When You Have Alzheimer's In The Family?

It seems that the older we get, the more people we know who have been diagnosed with Alzheimer's. Should we panic if a family member gets it? Will it increase our chances?

“People think that if their dad or aunt or uncle had Alzheimer's disease, they are doomed. But, no, that's not true,” says Dr. Gad Marshall, assistant professor of neurology at Harvard Medical School. “Even though family history adds to the overall risk, age still usually trumps it quite a bit. It means your risk is higher, but it's not that much higher, if you consider the absolute numbers.”

What Are My Chances If My Family Has A History?

If you have a close relative who has been diagnosed with Alzheimer's disease—the most common form of dementia in older adults—studies say your risk increase by about 30%. This may sound like a scary number, but it's a relative risk increase. This means a 30% hike in your existing risk.

At age 65, the risk of being diagnosed with Alzheimer's is 2% per year, this means you have a 98% chance of not developing Alzheimer's. When you look at the 30% increase in your existing risk, you now have a 2.6%. That means going from 20 cases in a group of 1,000 to 26 in 1,000. “So the absolute increase is relatively small,” Dr. Marshall says.

Aging raises the chance of Alzheimer's more than family history. People in their 70s have a 5% chance of being diagnosed; more than twice that of people in their 60s. Family history would raise this by the same 30%, from 5% to 6.5%. So the absolute change is relatively small.

Should You Get Genetic Testing?

After hearing that a relative is diagnosed with dementia later in life, family members often wonder if they should be tested for the “Alzheimer's gene.” The quick answer is no. “It can be a quick no or a long no, with more explanation, but the answer is nearly always no,” Dr. Marshall says. “It's not going to be helpful, since it won't tell you whether you will develop the disease. It will only tell you if you are at a greater risk.”

When Alzheimer's disease begins later in life; the vast majority of cases; a gene called apolipoprotein E (APOE4) is associated with greater risk for dementia. If you inherit one copy of APOE4, your risk triples. If you have two copes, your risk is 10 to 15 times higher, but this is rare.

But, having APOE4 does not mean you will definitely develop dementia. Among people who age normally into their 70s, about 25% still have one or more copies of the risk gene. And, just because you don't have the APOE4, you're still not guaranteed of not developing Alzheimer's, about 35% of the people who don't have the gene still develop it.

This means that if genetic testing reveals you have one or two copies of the APOE4, it will not tell you what you really want to know: will you get Alzheimer's disease or not? Knowing that you have the risk gene can instill fear and negatively influence your life decisions.

Genetic counselors discourage testing in people with close relatives who developed Alzheimer's disease later in life. “Having the gene says you have a higher risk, but it does not mean that you will get dementia,” Dr. Marshall emphasizes.

What To Do If Someone In Your Family Is Diagnosed With Alzheimer's?

  • Contact the Alzheimer's Association (www.alz.org). Find out about resources available to help you and your family. State and county agencies may also help.
  • Plan for the future. This includes legally designating someone to make health care and financial decisions for the affected person when he or she can't.
  • Investigate long-term care options. Nursing care is expensive and finding a good place can take time. Start early.
  • Take care of physical health. People with dementia who live a healthy lifestyle tend to progress more slowly to the later stages.
  • Steer away from genetic testing. Even if you have the APOE Alzheimer's risk gene, it rarely means you will develop dementia later in life.

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