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 Alzheimers disease, according to the Alzheimers 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.

The genetic factor

Theres a lot that scientists still dont know about Alzheimers, and that includes how much of a persons risk depends on genetics.

When diagnosing early-onset Alzheimers disease, which the National Institute on Aging estimates affects less than 5 percent of all Alzheimers 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, its likely that youll develop early-onset Alzheimers.

Nonetheless, if a grandparent or loved on in your family developed Alzheimers later in life, your risks are less understood. The most common gene associated with late-onset Alzheimers disease is called apolipoprotein E (APOE), namely APOE e4, according to the Mayo Clinic. Although genetics play a role in late-onset Alzheimers, 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 Alzheimers 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 Alzheimers 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 whos 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 its a far more effective strategy to try to protect a healthy brain before cognitive decline and Alzheimers disease are present.

A recent study from the University of California-San Francisco suggests that maintaining a healthy lifestyle could prevent as many as 3 million Alzheimers 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 Alzheimers 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 Alzheimers 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 youre worrying about your risk of Alzheimers 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 Alzheimers patients.

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 Alzheimers, Small said. These dietary changes dont 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: Theyre 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 its never too early, and its never too late, Small said.