Alzheimer’s disease represents a personal health crisis, but it’s also a family concern. What does it mean for your children or siblings if you are diagnosed with Alzheimer’s? What does it mean for you if a close relative develops the condition?

Dementia affects the man diagnosed but also raises fears for siblings and children. Here are the facts.

“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.”

Family history by the numbers

Studies of family history say that if you have a close relative who has been diagnosed with Alzheimer’s disease—the most common form of dementia in older adults—your risk increases by about 30%. This is a relative risk increase, meaning a 30% hike in your existing risk.

If you are age 65, the risk of being diagnosed with Alzheimer’s is 2% per year, although this also means a 98% chance per year of not developing Alzheimer’s. In absolute numbers, a 2% annual risk means that two out of 100 65-year-olds will develop dementia every year.

Family history raises the 2% annual risk by about 30%, to 2.6% per year. That means going from 20 cases in a group of 1,000 to 26 in 1,000, or six additional cases in 1,000. “So the absolute increase is relatively small,” Dr. Marshall says.

Age 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 raises this by 30%, from 5% to 6.5%. Again, the absolute change is relatively small.

Genetic testing not helpful

When a relative is diagnosed with dementia later in life, family members often wonder if they should be tested for the “Alzheimer’s gene.” The short 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 or lower risk.”

For more information click Harvard health publication