Preventive Maintenance For the Brain

If it seems you're forgetting more as you grow older, you are. Like most other organs in the body, the brain gets smaller as we age, leading to a decline in memory, decision-making ability and verbal skills. That doesn't necessarily mean that you're on a steep downhill slide toward certain dementia, say experts. Growing evidence suggests there are steps you can take to better the odds of preserving your brainpower and protecting it against disease.

Two avenues for boosting cognition -- challenging your brain and exercising your body -- have drawn considerable scientific research.

Just last week a massive review of the scientific data, published online, found that getting lots of physical activity and reducing your risk of heart disease -- by cutting cholesterol and blood pressure levels, for example, or losing weight -- are among the best ways to maintain a healthy brain. The study, funded by the National Institutes of Health (NIH), also found that increased mental activity throughout life appears to preserve brainpower.

Through its "Maintain Your Brain" campaign, the Alzheimer's Association urges people to regularly engage in mentally stimulating activities. These may involve doing logic puzzles like Sudoku, reading an entire newspaper daily or going to a museum -- anything that takes you outside your normal range of thinking, said Elizabeth Edgerly, a clinical psychologist who helped develop the campaign.

Mental challenges such as these, researchers theorize, build neural pathways in the brain, buffering against age-related loss and possibly an assault by disease. Some researchers have hypothesized that persistent, effortful mental activity might even retard underlying disease.

Meanwhile, evidence that physical activity may protect against cognitive loss impresses other experts on aging. A recent study that followed more than 1,700 normal seniors for six years found those who exercised the most -- at least three times a week -- were least likely to develop Alzheimer's disease. One theory, based partly on animal research, is that physical exercise may improve blood flow and oxygen delivery to the brain and increase substances that promote the growth of tissue and blood cells in the hippocampus, a region critical to memory.

But even if mind games or physical activity confer a protective benefit -- scientists say proof is still far off -- there are limits: The most determined personal efforts won't override a strong genetic predisposition to Alzheimer's, say experts. (But not every mental lapse is a sign of dementia. See "Is It Normal? Or a Warning Sign?" )

Other factors may also affect brain integrity, including diet (for brain health, nutritionists suggest a diet low in saturated fats and rich in vegetables, fruit and fish with omega-3 fatty acids), social life (an active one is thought to improve immunity and reduce inflammation, believed to play a role in Alzheimer's) and health problems like diabetes and heart disease.

Those issues aside, a major question remains: If exercise is protective, what kind is best and at what dose? No one can say.

"You can say with conviction that if a person decides to exercise a certain amount every day or week, that it will help their heart and that it might help their head," said Marcelle Morrison-Bogorad, director of the neuroscience and neuropsychology of aging program at the National Institute on Aging (NIA). But whether one form of exercise is superior-- whether, say, aerobic exercise beats non-aerobic -- isn't yet known, any more than whether playing chess or listening to classical music will give you more protection than playing Scrabble or going to a rock concert.

Mental Case

The idea that challenging the brain may help stave off dementia has intrigued many researchers. Defining what constitutes "challenging," though, is difficult, said Edgerly. "If you think of each of us as individuals, what's mentally stimulating to me might be really easy for you and not make you break a cognitive sweat," she said.

The Religious Orders Study, which began in 1993 and includes more than 1,000 nuns, priests and brothers across the country, has found that those who engage more often in reading, puzzles and processing information have a 47 percent lower risk of Alzheimer's disease than those who do little or none. The NIA is funding the study.

A research review published in the journal Psychological Medicine found that people who have a significant "brain reserve," or intellectual base, have a much lower risk of developing dementia. "In virtually every study in which we've looked, the more education you have, the lower the prevalence of dementia in that group," said Steven DeKosky, director of the Alzheimer's Disease Research Center at the University of Pittsburgh.

Hybrid activities -- those combining a mental stimulus with some other action -- are also the subject of scientific interest. "Some of the strongest evidence is for activities that involve physical, mental and social at the same time," said Edgerly. Examples include social dancing and coaching or refereeing a team sport, she said.

A recently published study by Sweden's Karolinska Institute offers a case in point. Researchers who followed 776 normal seniors aged 75 and over for six years found that those who said they took part regularly in mental, physical or social activities had a lower risk of dementia; those who combined all three had the lowest risk. Activities that seemed to confer more protection included political and cultural involvement, attending courses, going to the theater or concerts, traveling, being engaged in charity or church activities, and playing music with others.

Getting Physical

Advocates of physical activity to protect against cognitive loss point to a solid -- and increasing -- body of evidence. The just-released NIH review found that, of a host of factors found to confer protection -- including higher education, moderate alcohol use and having a strong social network -- exercise was most impressive. The review reported that three very large trials "found that elders who exercise are less likely to experience cognitive decline."

A study last month in the Annals of Internal Medicine followed 1,740 people over age 65 for six years. The participants, all of whom had normal cognitive function at the start, initially reported how often they exercised for at least 15 minutes a day -- everything from stretching and walking to cycling, weight training and aerobic exercise. Every two years, they were given tests to determine their cognitive and physical functioning, and were also asked to assess their general health.

Those who exercised the most -- at least three times a week -- had the lowest risk of Alzheimer's, 32 percent less than the others. Also, those who started out with the lowest level of exercise benefited the most. That suggests it's especially important for sedentary people to get moving, said Eric Larson, director of the Center for Health Studies at Group Health Cooperative, a nonprofit health system in Seattle.

"I think you can make a conclusion that if you're active . . . at an age of 65 or greater, you have an association of a lower risk of Alzheimer's disease and dementia," said Larson.

The finding is consistent with some observations of brain biology, said DeKosky. "There's no question from animal studies that you can even see brain changes in certain growth factors if the animals are forced to exercise," he said.

Other researchers -- Paul Aisen, director of the Memory Disorders Program at Georgetown University Hospital, for one -- aren't as convinced that exercise increases blood flow or that there's a link between blood flow and brain function. Both DeKosky and Aisen agree that exercise has been proven beneficial for cardiovascular health and that it makes people feel better and more alert. But most exercise studies haven't come up with enough data to prescribe a "dose" of activity that's protective. And there are other unknowns. For instance, said Morrison-Bogorad, "we don't know whether you can stop exercise for a few weeks and keep the benefit that you had before you stopped."

Seeking Answers

Researchers are continuing to explore whether exercising the brain or body can have any positive impact on brain function, but definitive proof may never be produced, said DeKosky. Rigorous clinical studies that compare one intervention against another -- for example, a drug against a dummy pill -- guard against bias by making sure neither the physician nor patient knows who is getting what. That's not possible in exercise studies.

In addition, testing whether exercise improves brain health could require huge trials lasting decades -- an expense hard to justify when it's already known that physical activity has health benefits, said many researchers.

The NIA is funding two small studies -- which could become larger trials -- looking at the effects of exercise on older people's ability to make decisions and whether exercise can improve mild cognitive impairment.

For now, say experts, it's not a bad idea to hedge your bets by exercising mind and body. "It doesn't mean you won't get [Alzheimer's disease]," said DeKosky. "What it does is decrease the statistical possibility that you will get it," he said.

Even in the absence of firm evidence, he and others say, there's no harm done by that prescription.

"Fortunately, we're not asking people to do something potentially dangerous, unless they are overdoing it," said Dallas Anderson, program director for population studies in the Dementias of Aging Branch at the NIA. Even better, "the Larson study suggests that only a moderate amount of exercise would be needed, which is probably reassuring to a lot of people." ·

Alicia Ault last wrote for Health about an alternative to hip replacement surgery. Join Molly V. Wagster of the Neuroscience and Neuropsychology of Aging Program at NIA for a Live Online chat today at noon at www.washingtonpost.com. Comments: health@washpost.com.