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

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?

"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 Alzheimer's disease that 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 copies, your risk is 10 to 15 times higher (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. Nor does the absence of APOE4 protect you: about 35% of people with Alzheimer's don't have one of the risk genes.

This means that if genetic testing reveals that you have one or more copies of APOE4, it will not tell you what you really want to know: will you definitely get Alzheimer's disease—or will you not? Knowing that you have the risk gene could 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.

The way you live, what you eat and drink, and how you treat your body affect your memory as well as your physical health and wellbeing. Here are five things you can do every day to keep mind and body sharp.

Manage your stress. The constant drumbeat of daily stresses such as deadline pressures or petty arguments can certainly distract you and affect your ability to focus and recall. But the bigger problem is an ongoing sense of extreme anxiety—that can lead to memory impairment. If you don’t have a strategy in place for managing your stress, protecting your memory is one reason to get one. Deep breathing, meditation, yoga, and a “mindful” approach to living can all help.

Get a good night’s sleep. People who don’t sleep well at night tend to be more forgetful than people who sleep soundly. A good night’s sleep is essential for consolidating memories. The most common reason for poor sleep is insomnia—difficulty falling asleep or staying asleep. Unfortunately, many medicines used to treat insomnia can also impair memory and general brain function. That’s why it’s best to try improving your sleep habits first and turn to medication only if those steps don’t help. If you do need sleep aids, use the lowest dose for the shortest time needed to get your sleep back on track.

If you smoke, quit. Easier said than done, certainly, but if you need additional motivation, know that smokers have a greater degree of age-related memory loss and other memory problems than nonsmokers. People who smoke more than two packs of cigarettes a day at midlife have more than double the risk of developing dementia in old age compared with nonsmokers. However, those who stop smoking by midlife and those who smoke less than half a pack a day have a similar a risk of dementia as people who have never smoked.

If you drink alcohol, do so moderately. Drinking too much alcohol increases the risk for memory loss and dementia. People with alcoholism have difficulty performing short-term memory tasks, such as memorizing lists. Another type of memory loss associated with alcohol use is called Korsakoff’s syndrome. In this condition, long-term vitamin B1 deficiency combined with the toxic effects of alcohol on the brain can trigger sudden and dramatic amnesia. In some cases this memory loss is permanent, but if caught early, can be reversed to some degree.

Protect your brain from injury. Head trauma is a major cause of memory loss and increases the risk of developing dementia. Always use the appropriate gear during high-speed activities and contact sports. Wear seat belts when riding in motor vehicles. Car accidents are by far the most common cause of brain injury, and wearing seat belts greatly reduces the chances of severe head injury. Wear a helmet when bicycling, riding on a motorcycle, in-line skating, and skiing.

Original article is at Harvard Health Publishing