a1 Center for Human Nutrition, Department of International Health, Johns Hopkins Bloomberg School of Public Health, 615 N Wolfe Street E2610, Baltimore, MD 21205, USA
a2 Department of Epidemiology, School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
a3 Carolina Population Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
a4 Department of Family Medicine, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
a5 Department of Biostatistics, School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
Objective Recent research indicates that n–3 fatty acids can inhibit cognitive decline, perhaps differentially by hypertensive status.
Design We tested these hypotheses in a prospective cohort study (the Atherosclerosis Risk in Communities). Dietary assessment using a food-frequency questionnaire and plasma fatty acid exposure by gas chromatography were completed in 1987–1989 (visit 1), while cognitive assessment with three screening tools – the Delayed Word Recall Test, the Digit Symbol Substitution Test of the Wechsler Adult Intelligence Scale–Revised and the Word Fluency Test (WFT) – was completed in 1990–1992 (visit 2) and 1996–1998 (visit 4). Regression calibration and simulation extrapolation were used to control for measurement error in dietary exposures.
Setting Four US communities – Forsyth County (North Carolina), Jackson (Mississippi), suburbs of Minneapolis (Minnesota) and Washington County (Maryland).
Subjects Men and women aged 50–65 years at visit 1 with complete dietary data (n = 7814); white men and women in same age group in the Minnesota field centre with complete plasma fatty acid data (n = 2251).
Results Findings indicated that an increase of one standard deviation in dietary long-chain n–3 fatty acids (% of energy intake) and balancing long-chain n−3/n–6 decreased the risk of 6-year cognitive decline in verbal fluency with an odds ratio (95% confidence interval) of 0.79 (0.66–0.95) and 0.81 (0.68–0.96), respectively, among hypertensives. An interaction with hypertensive status was found for dietary long-chain n–3 fatty acids (g day−1) and WFT decline (likelihood ratio test, P = 0.06). This exposure in plasma cholesteryl esters was also protective against WFT decline, particularly among hypertensives (OR = 0.51, P < 0.05).
Conclusion One implication from our study is that diets rich in fatty acids of marine origin should be considered for middle-aged hypertensive subjects. To this end, randomised clinical trials are needed.
(Received August 04 2006)
(Accepted February 05 2007)