Which would you rather have during old age: a sharp mind or good physical health? The assumption behind this conundrum may be missing the point— that with healthy lifestyle choices, you can have both.

More than 5 million Americans are currently living with Alzheimer’s disease, according to the Alzheimer’s Association, and one-third of American seniors die with the disease or another form of dementia. For those elders and the people who love them, the forgetfulness and slow descent into complete dependency can not only be costly and heartbreaking, but frightening, particularly when relatives are concerned about inheriting the disease themselves.

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The genetic factor

There’s a lot that scientists still don’t know about Alzheimer’s, and that includes how much of a person’s risk depends on genetics.

When diagnosing early-onset Alzheimer’s disease, which the National Institute on Aging estimates affects less than 5 percent of all Alzheimer’s patients, doctors have observed a genetic link. Early-onset, which occurs in people ages 30 to 60, is due to one of several genetic mutations. If one of your parents carries the mutation for the disease, you have a 50 percent chance of inheriting it. If inherited, it’s likely that you’ll develop early-onset Alzheimer’s.

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Nonetheless, if a grandparent or loved on in your family developed Alzheimer’s later in life, your risks are less understood. The most common gene associated with late-onset Alzheimer’s disease is called apolipoprotein E (APOE), namely APOE e4, according to the Mayo Clinic. Although genetics play a role in late-onset Alzheimer’s, the issue is clouded by several factors—  including the influence of lifestyle.

The lifestyle factor

Scientists have found that the amyloid plaques and tangles in the brain, believed to be responsible for producing the symptoms of Alzheimer’s disease, can be detected in brain scans long before a person is symptomatic, sometimes even decades before.

“When I tell people that, it scares them,” said Dr. Gary Small, director of the UCLA Longevity Center and co-author of “The Alzheimer’s Prevention Program: Keep Your Brain Healthy for the Rest of Your Life.”

“On the other hand, this [knowledge] offers us a huge opportunity to find out who’s at risk and to identify candidates for early intervention,” Small said.

Waiting until a patient is symptomatic limits the approaches that can have a considerable positive impact. Small and a growing number of experts believe it’s a far more effective strategy to try to protect a healthy brain before cognitive decline and Alzheimer’s disease are present.

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A recent study from the University of California-San Francisco suggests that maintaining a healthy lifestyle could prevent as many as 3 million Alzheimer’s cases globally and up to 492,000 cases in the United States.

The list of preventive lifestyle changes is relatively long, but Dr. Small suggests starting with four:

1. Move your body.

Studies on how physical fitness may impact Alzheimer’s risk have offered some of the most compelling evidence that prevention is possible. Scientists believe exercise benefits the brain in more than one way.

“What happens when you get cardiovascular exercise is that your heart pumps oxygen and nutrients to your brain,” Small said. “But it also causes your body to produce something called BDNF, or brain-derived neurotrophic factor, which is kind of like a fertilizer for your brain, getting it to sprout new cells.”

In addition to BDNF, the brain produces endorphins during exercise. These hormones act as mood elevators, analgesics and anti-inflammatories— all qualities believed to impact brain health and slash Alzheimer’s risk.

2. Challenge your mind.

Crossword puzzles, learning a new language, playing trivia with friends— these mental activities can maintain and even improve brain health. Using techniques that sharpen your memory to combat age-related brain changes may also stave off those “senior moments.”

“The one we introduced in one of our books is ‘Look, Snap, Connect,’” Small said. “’Look’ is a reminder to focus your attention; ‘snap’ is a reminder to create a mental snapshot; and finally, ‘connect’ is a way to link up those mental snapshots so they have meaning. If something is meaningful, it will be memorable.”

3. Reduce stress.

Stress is a given in life. We may not be able to eliminate it, but we can manage it. And if you’re worrying about your risk of Alzheimer’s disease, Small has some advice: Stop. Worrying itself is a form of stress, so worrying about memory loss could actually worsen your chances of maintaining a sharp mind.

As with other prevention strategies, stress relief could even be effective for people already suffering from dementia. A recent trial from the University of California, Los Angeles and the Buck Institute for Research on Aging found that meditating twice a day for stress relief can help reverse some memory loss in Alzheimer’s patients.

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4. Eat right.

Past research has linked obesity to a greater risk of dementia. A recent observational study published in the British Medical Journal suggests that dementia risk is threefold for people who are obese in their 30s.

Eating more fruits and vegetables, increasing your intake of Omega 3 fats, and managing your weight through calorie control are also good habits that may protect against Alzheimer’s, Small said. These dietary changes don’t only have the potential to change your brain health— they can also help improve your physical health and quality of life.

And remember: not smoking, getting plenty of rest, maintaining proper medical care and protecting your head from injuries can also keep your mind healthy as you age.

The key takeaway from these tips: They’re as good for your physical health as your mental acuity. And according to Small, now is the best time to get started, regardless of your age.

“I like to say it’s never too early, and it’s never too late,” Small said.