High dietary and plasma levels of the omega-3 fatty acid docosahexaenoic acid are associated with decreased dementia risk: the Rancho Bernardo study.

Abstract

This study examined the association of plasma DHA, dietary DHA, and fish intake with dementia and Alzheimer's Disease (AD) in older adults. Case-cohort study. Clinic visit in 1991-93. 266 community dwelling men and women aged 67-100 years (mean=80.2). Participants had neurological and neuropsychological evaluations for dementia in 1991-93. Plasma DHA was measured in blood samples obtained at that visit. Dietary intakes of DHA and fish were obtained from an earlier (1988-91) visit. Three DHA exposure variables were used in separate analyses; plasma DHA, dietary DHA, and consumption of cold-water fish. All-cause dementia included AD and other types of possible or probable dementia. Among these 266 participants, 42 had dementia and 30 had possible or probable AD. Plasma DHA in the highest tertile was associated with a 65% reduced odds of all-cause dementia (95% CI: 0.17, 0.92) and a 60% reduced odds of AD (95% CI: 0.15, 1.10). Dietary DHA in the highest tertile was associated with a 73% reduced odds of all-cause dementia (95% CI: 0.09, 0.79) and a 72% reduced odds of AD (95% CI: 0.09, 0.93). Fish intake had similar, though not significant, reduced odds of dementia (OR = 0.51; 95% CI: 0.20, 1.32) and AD (OR = 0.55; 95% CI: 0.20, 1.48). Plasma and dietary DHA appear to protect against dementia. Increasing DHA intake from marine sources may be recommended for reducing dementia risk.