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Another crucial finding from the Nun Study came in 1997, by which time Snowdon had accumulated some 100 brains for analysis. He and neurologist Dr. William Markesbery, director of the Alzheimer's Disease Research Center at the University of Kentucky, were intrigued by an idea advanced by other researchers that strokes and other brain trauma might contribute to the dementia of Alzheimer's disease. Selecting only the brains of sisters who had earned a bachelor's degree--to eliminate any differences attributable to education--they found that among nuns with physical evidence of Alzheimer's in the brain, those who had evidence of strokes as well almost inevitably showed outward symptoms of dementia. But only half the nuns without strokes were comparably afflicted. Says Suzman, of the National Institute on Aging: "This is one of the first studies to look at the cardiovascular component of Alzheimer's disease."
It's also one of the first to suggest a way to stave off Alzheimer's symptoms. "If your brain is already progressing toward Alzheimer's," says Snowdon, "strokes or head trauma [which can produce similar kinds of brain damage] can put you over the edge." His advice: wear a helmet while biking, motorcycling or playing contact sports; buckle your seat belt; and drive a car with air bags. Meanwhile, keep strokes at bay by keeping your cardiovascular system in shape: avoid tobacco, get regular exercise and eat a balanced, healthy diet.
Diet may play a role in Alzheimer's in other ways as well. In 1998 British researchers announced that Alzheimer's victims have low concentrations in their blood of the nutrient folate, also called folic acid. That's an intriguing result, especially in light of other studies showing that folic acid deficiency plays a role in some forms of mental retardation in children and in cognitive problems in adults. So Snowdon began looking at levels of folic acid, along with 18 other micronutrients (including beta carotene, magnesium, zinc and cholesterol) in blood samples of 30 sisters who had died since the study began.
Sure enough, he found that the sisters with high folate levels showed little evidence of Alzheimer's-type damage in their brain after death. This makes a certain amount of sense; folate tends to counteract the effects of homocysteine, an amino acid produced in the body that has been implicated in cardiovascular disease. Plenty of folate in the blood would thus mean less chance of stroke--and might even protect brain cells from damage by homocysteine in the brain.
Unfortunately, the other micronutrients haven't panned out so well. It makes sense that antioxidants like vitamin E and vitamin C, which soak up cell-damaging "free-radical" molecules in the body, would protect against cell destruction. Although vitamin E looked promising in an earlier study, neither substance had an obvious effect on the Notre Dame sisters. Nor, on the other side of the equation, did mercury or aluminum in the diet, both of which had been implicated in earlier studies as possible triggers for Alzheimer's.