Consumption of fish and n-3 fatty acids and risk of incident Alzheimer disease.

BACKGROUND Dietary n-3 polyunsaturated fatty acids improve brain functioning in animal studies, but there is limited study of whether this type of fat protects against Alzheimer disease. OBJECTIVE To examine whether fish consumption and intake of different types of n-3 fatty acids protect against Alzheimer disease. DESIGN Prospective study conducted from 1993 through 2000, of a stratified random sample from a geographically defined community. Participants were followed up for an average of 3.9 years for the development of Alzheimer disease. PATIENTS A total of 815 residents, aged 65 to 94 years, who were initially unaffected by Alzheimer disease and completed a dietary questionnaire on average 2.3 years before clinical evaluation of incident disease. MAIN OUTCOME MEASURES Incident Alzheimer disease diagnosed in a structured neurologic examination by means of standardized criteria. RESULTS A total of 131 sample participants developed Alzheimer disease. Participants who consumed fish once per week or more had 60% less risk of Alzheimer disease compared with those who rarely or never ate fish (relative risk, 0.4; 95% confidence interval, 0.2-0.9) in a model adjusted for age and other risk factors. Total intake of n-3 polyunsaturated fatty acids was associated with reduced risk of Alzheimer disease, as was intake of docosahexaenoic acid (22:6n-3). Eicosapentaenoic acid (20:5n-3) was not associated with Alzheimer disease. The associations remained unchanged with additional adjustment for intakes of other dietary fats and of vitamin E and for cardiovascular conditions. CONCLUSION Dietary intake of n-3 fatty acids and weekly consumption of fish may reduce the risk of incident Alzheimer disease.