Prevention

DHEA. Dehydroepiandrosterone (DHEA) is a male-like hormone in the body that declines with age. Some evidence suggests that it may help reduce mental decline in older women, but not in older men. Studies are under way. The hormone may, however, reduce HDL (the so-called good cholesterol) when taken in higher doses and its effect on cancer-cell growth is unknown. Some evidence indicates that high levels may increase cancer risk. In any case, DHEA is not regulated and brands vary widely in their content.

Dietary Factors

Because of differences in Alzheimer's disease rates among different populations, investigators are researching how diet can help in prevention. Caloric intake itself may play a role in brain health. In one study on animals, restricting calories below normal (but above starvation levels) helped prevent age-related nerve degeneration. However, that in patients with existing Alzheimer's, weight loss is a strong indicator of mental decline.

Fats and Oils. The following are some studies that suggest an association between fat and Alzheimer's disease:

• In China and Nigeria, where fat intake is low, the risk of developing Alzheimer's is 1% at age of 65 compared to 5% in the U.S.
• A study in the Netherlands reported an association between dementia and diets high in total fat, saturated fat, and cholesterol.
• A number of studies suggest that a high-fat high-calorie diet in people who carry the ApoE4 gene may confer a particularly high risk. For example, in one study, adults who carried the ApoE4 gene and whose diet consisted of 40% fat calories had 29 times the risk for Alzheimer's compared to non-ApoE4 carriers on the same high-fat diet.

Fish oil contains omega-3 fatty acids. These fatty acids are found in fish such as salmon, halibut, swordfish, and mackerel. In one study, eating oily fish at least once a week was associated with a lower risk for Alzheimer's disease. Studies indicate that a particular type of omega-3 fatty acid, called docosahexaenoic acid (DHA), may especially help protect the aging brain.