Fish are a primary source of long-chain omega-3 fatty acids, which may help delay cognitive aging. We pooled participants from the French Three-City study and four US cohorts (Nurses' Health Study, Women's Health Study, Chicago Health and Aging Project and Rush Memory and Aging Project) with diet and cognitive data (n = 23,688 Caucasians aged >/=65 years, 88% female, baseline year range, 1992-1999, median follow-up range, 3.9-9.1 years) to investigate the relation of fish intake to cognitive decline and examine interactions with Alzheimer's disease-related genes. We estimated cohort-specific associations between fish and change in composite scores of global cognition and episodic memory using linear mixed models, and pooled results using inverse-variance weighted meta-analysis. In multivariate analyses, higher fish intake was associated with slower decline in both global cognition and memory (P-trend </= 0.031). Consuming >/=4 versus <1 fish serving/week was associated with 0.018 (95% CI: 0.004, 0.032) standard units lower rate of memory decline; an effect estimate equivalent to that found for 4 years of age. For global cognition, no comparisons of higher versus low fish intake reached statistical significance. In this meta-analysis, increasing fish intake was associated with decreasing memory decline. We found no evidence of effect modification by Alzheimer's disease genes.Read less <