( P < 0.0001), alcohol intake ( P = 0.0006), and female gender ( P = 0.02), and decreased with intensive consumption of n-6 oils ( P = 0.02). The positive association between fi sh consumption and plasma DHA was highly signifi cant whatever the APOE genotype ( P < 0.0001) but stronger in APOE4 noncarriers than in carriers ( P = 0.06 for interaction). Plasma DHA increased signifi cantly with age ( P = 0.009) in APOE4 noncarriers only. These fi ndings suggest that dietary habits, gender, and APOE4 genotype should be considered when designing interventions to increase n-3 PUFA blood levels in older people. -Samieri, C., S. Lorrain, B. Buaud, C. Vaysse, C. Berr, E. Peuchant, S. C. Cunnane, and P. Barberger-Gateau. Relationship between diet and plasma long-chain n-3 PUFAs in older people: impact of apolipoprotein E genotype. Long-chain n-3 PUFAs [eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] could potentially exert a protective effect against brain aging due principally to their vascular, anti-infl ammatory, and neuroprotective properties ( 1 ). Accordingly, several epidemiological studies have observed an inverse association between habitual consumption of long-chain n-3 PUFAs or fi sh, their main dietary source, and risk of cognitive decline or dementia ( 1 ). However, this protective association may be limited to Abbreviations: 3C, Three-City; AD, Alzheimer's disease; ALA, ␣ -linolenic acid; APOE4 , 4 allele of the APOE gene; DHA, docosahexaenoic acid; EPA, eicosapentaenoic acid; FFQ, food frequency questionnaire; HR, hazard ratio; RCT, randomized controlled trial.