The numbers are frightening: Right now an estimated 47 million people around the world have Alzheimer's disease or another forms of dementia. By 2050, that number is expected to triple.

Anyone who has witnessed a loved one lose their memories and maybe even stop recognizing their own family members likely dreads the disease more than a heart attack or cancer (both of which are far more likely to kill you). There is no cure for the disease — but research has shown there are steps you can take to minimize your risk.

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Heather Snyder, PhD, director of medical and scientific operations for the Alzheimer's Association, and colleagues recently evaluated reams of published studies and other data on what works. More research is needed on Alzheimer’s prevention, but for now, Snyder says, adopting (or continuing) these four habits is strongly linked with lowering the risk of developing dementia if your brain is healthy now. If you've been lax about these health measures, she says, starting now can still make a difference.

Exercise

Of all the lifestyle changes evidence points to for preserving brain health, "physical activity would probably be the strongest," Snyder says. Numerous studies have found that physical activity, even at moderate levels, can protect against dementia.

Lifelong exercise is ideal, Snyder says. But it’s never too late to start. Many other studies have found that healthy seniors who were inactive but then started an exercise program had better cognitive functioning.

In one study, researchers compared 60 older adults who did moderate aerobic activity three times a week for a year with another 60 who stretched three times a week for a year. Those who did aerobic activity (which can include cycling, jogging, walking and swimming) had a 2 percent increase in the volume of the brain's hippocampus, which is important for memory functioning. The stretchers lost volume in that brain.

No one is certain how much physical activity or what type or intensity is best for brain health, Snyder says. Experts also don’t know at which point in your life exercise is most important. So the best advice for now is to keep moving or get moving.

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Keep learning

If you graduated from college or have an advanced degree, you are less likely to get dementia than people with less education, research has found. Even so, no matter what your level of formal education, if you keep on learning as an adult, you can reduce your risk, Snyder says. "As someone continues to learn, their brains are making new connections," she says.

In one study that looked at nearly 2,000 adults age 70 and older, most with normal cognition, researchers found higher education was linked with better brain functioning — but so was staying mentally engaged during midlife and later life.

Learning something new is important, Snyder says. Reading the same book over and over doesn't produce the same benefits as plowing through something you haven’t seen before, she says.

The options for lifelong learning are endless. Take a class at a community college class or the YMCA, join a new interest group, learn a language from an online course or audio tapes, take up a musical instrument or work your way through some of the classics.

Manage chronic diseases

High blood pressure and diabetes both increase the risk of dementia.

Having high blood pressure at midlife, defined as ages 40 to 64, has been linked to a higher risk of dementia in later years.

In some research, people who had diabetes at the start of the study had double the chances of developing dementia as they aged. Scientists aren't sure why diabetes may boost dementia risk. One possibility is that the high blood sugar levels seen in people with poorly controlled diabetes may adversely affect brain cells and blood vessels, including those in the brain.

Avoiding these conditions altogether is best for reducing your dementia risk, of course.  Next best, Snyder says, is managing them. Medications and lifestyle changes, such as getting more exercise or tweaking your diet, can help keep blood pressure out of the danger zone. Diabetes can also be kept under control with lifestyle changes and medications.

Related: Warning: You Might Have Diabetes and Not Know It

Protect your head

Head injury and dementia have been linked in a number of studies, Snyder says. In one, researchers evaluated more than 188,000 U.S. veterans age 55 and older. Those with a history of traumatic head injuries were 60 percent more likely to develop dementia over the seven-year study period than those without that history. Experts don’t yet have a proven explanation for the link.

Of course, head injuries are accidental, but to avoid them, use your head: If you’re a cyclist or motorcycle rider, a horseback rider or someone who plays a contact sport, always wear a helmet. In your car — or in someone else’s (including a taxi) — wear your seat belt. Don't take chances on ladders, and take steps to fall-proof your home and accident-proof your bathroom. Older folks can also take these steps to lower their fall risk.

Follow the “recipe” for dementia risk reduction

Growing evidence suggests these healthy habits work best together, Snyder says. For instance, exercise may help with weight control, and that, in turn, may help prevent high blood pressure or diabetes.

What's also known: if something you're doing is good for your heart, it's likely to be very good for your brain, too, she says.

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Kathleen Doheny is a Los Angeles journalist specializing in health, behavior and fitness topics.