So how’s your memory? Pretty normal for your age?

Uh-oh.

“Normal” is not ideal when it comes to the ability to form and retain new memories as we age, said Dr. Riley McCarten, an associate professor in the Department of Neurology at the University of Minnesota.

“As people get older, particularly in late life, 80s and older, it may in fact be normal to have significant memory loss,” McCarten said. “But that doesn’t mean it’s healthy.”

A healthy aging brain remains fully functional, McCarten said; it might process information more slowly, but memory remains intact, as does the ability to learn and retain new information.

Still, age is the greatest risk factor for Alzheimer’s Disease, the most common form of dementia, said Michelle Barclay, vice president of program services for the Azheimer’s Association Minnesota-North Dakota (www.alz.org/mnnd). Among the aging, Alzheimer incidence rises sharply, she said, affecting about one in 10 people at age 65 and nearly half of 85-year-olds.

The disease remains incurable for now, its causes mysterious. Although Alzheimer’s is partly linked to heredity, many people with slightly higher genetic risk factors never develop the disease. Healthy habits may help postpone its onset or slow its progress, if not prevent it, Barclay said. “I think a better term would be risk reduction.”

But exactly which habits best reduce the risk, unfortunately, is still something of a guessing game. “I don’t think we really understand why some people get Alzheimer’s Disease and others don’t,” Barclay said. A couple of years ago, a team from Duke University combed through 25 years of research, examining nearly 300 studies on various interventions that might forstall cognitive decline, from ginkgo biloba supplements to crossword puzzles, and found little solid proof that any of them worked. Researchers have found some evidence of benefits from exercise and formal brain-training programs. (Nicotine users, perhaps surprisingly, are less likely to get dementia, but McCarten suspects that might be because they die of other things first.)

Studies can take years, and meanwhile an epidemic is looming. In 2012, 5.4 million Americans had Alzheimer’s, a number expected to triple by 2050. Yet funding for Alzheimer’s research, unlike that for other diseases, has not increased, Barclay said (and deaths from other diseases have declined, while deaths from Alzheimer’s have increased 66 percent).

Dr. Gary Small, a professor at the University of California-Los Angeles Medical Center and author of “The Alzheimer’s Prevention Program” (Workman Publishing, 2012) isn’t waiting around.

“There’s compelling science that tells me there’s a lot we can do right now,” he said. “Frankly, I don’t want to wait 20 years for someone to tell me, ‘Geez you should have been doing this.’”

So until more research comes in, the following might help (or at least can’t hurt).

Get your exercise

“It’s the very last thing that people want to hear,” Barclay said. “It doesn’t come in a pill. It’s not fun. But exercise is the No. 1 protector.”

You needn’t sign up for a triathalon; three brisk half-hour walks a week may be sufficient. “There’s no measurable difference in brain health, or even heart health, for a high level of physical activity,” McCarten said. “But there is a measurable difference between those who do moderate exercise and those who are sedentary.”

Follow a healthy diet

Vegetables are good for your brain; refined sugars and processed foods not so much. “An unhealthy diet is correlated with not just poor brain health but poor cardiovascular health, “ McCarten said. “And if heart and blood vessels aren’t working well, your brain’s going to suffer.”

Alzheimer’s risk doubles for people who are overweight, triples for the obese. “Losing weight actually improves memory performance,” Small said.

Stimulate your brain

Education (not just in school, but lifelong) seems to reduce the risk of Alzheimer’s, perhaps by creating more neural pathways that can take over if some are damaged. “There could be plaque in your brain, but you’re rerouting,” Barclay said.

Learning a new skill — a musical instrument or language, chess, dancing — may be helpful, but only if you enjoy it, McCarten said. “If it’s stressful, that’s not healthy,” he said. “I think stress is bad, for your mental health and your brain health.” What about the often-advised crosswords and Sudoku? Again, do them if you enjoy them, but don’t bother if they feel like homework.

So you say you’ve been losing your keys a lot lately, or walking into rooms and forgetting what you went there for? You probably needn’t worry that you’re sliding into dementia, McCarten said.

“Isolated events aren’t what concern me nearly as much as family members who recognize a persistent problem that is getting progressively worse,” he said. “It’s people forgetting names, repeating themselves. They’ll ask ‘When’s the doctor’s appointment?’ then ask it again five minutes later and 10 minutes later, the same identical question. If I picked three things that tend to be hallmarks of somebody who may be developing a problem, it’s repeating themselves, relying more on notes and calendars [for basic tasks], and getting lost driving in an otherwise familiar area.”

After all, McCarten said, his wife loses her keys all the time. “We’re looking for them almost every day,” he said. “On the other hand, she’s never forgotten anything I’ve ever said.” â–¡