To illustrate the impact of combining 24 h recall (24hR) and FFQ estimates using regression calibration (RC) and enhanced regression calibration (ERC) on diet–disease associations.

Wageningen area, the Netherlands, 2011–2013.

Five approaches for obtaining self-reported dietary intake estimates of protein and K were compared: (i) uncorrected FFQ intakes (FFQ); (ii) uncorrected average of two 24hR ( $\overline {\rm R}$ ); (iii) average of FFQ and $\overline {\rm R}$ ( ${\overline {\rm F}}\,\overline {\rm R}}$ ); (iv) RC from regression of 24hR v. FFQ; and (v) ERC by adding individual random effects to the RC approach. Empirical attenuation factors (AF) were derived by regression of urinary biomarker measurements v. the resulting intake estimates.

Data of 236 individuals collected within the National Dietary Assessment Reference Database.

Both FFQ and 24hR dietary intake estimates were measured with substantial error. Using statistical techniques to correct for measurement error (i.e. RC and ERC) reduced bias in diet–disease associations as indicated by their AF approaching 1 (RC 1·14, ERC 0·95 for protein; RC 1·28, ERC 1·34 for K). The larger sd and narrower 95% CI of AF obtained with ERC compared with RC indicated that using ERC has more power than using RC. However, the difference in AF between RC and ERC was not statistically significant, indicating no significantly better de-attenuation by using ERC compared with RC. AF larger than 1, observed for the ERC for K, indicated possible overcorrection.

Our study highlights the potential of combining FFQ and 24hR data. Using RC and ERC resulted in less biased associations for protein and K.

Recent research indicates that n–3 fatty acids can inhibit cognitive decline,perhaps differentially by hypertensive status.

We tested these hypotheses in a prospective cohort study (the AtherosclerosisRisk in Communities). Dietary assessment using a food-frequencyquestionnaire and plasma fatty acid exposure by gas chromatography werecompleted in 1987–1989 (visit 1), while cognitive assessment withthree screening tools – the Delayed Word Recall Test, the DigitSymbol Substitution Test of the Wechsler Adult IntelligenceScale–Revised and the Word Fluency Test (WFT) – wascompleted in 1990–1992 (visit 2) and 1996–1998 (visit4). Regression calibration and simulation extrapolation were used to controlfor measurement error in dietary exposures.

Four US communities – Forsyth County (North Carolina), Jackson(Mississippi), suburbs of Minneapolis (Minnesota) and Washington County(Maryland).

Men and women aged 50–65 years at visit 1 with complete dietarydata (n = 7814); white men and women insame age group in the Minnesota field centre with complete plasma fatty aciddata (n = 2251).

Findings indicated that an increase of one standard deviation in dietarylong-chain n–3 fatty acids (%of energy intake) and balancing long-chain n−3/n–6 decreased the risk of 6-year cognitive decline inverbal fluency with an odds ratio (95% confidence interval) of 0.79(0.66–0.95) and 0.81 (0.68–0.96), respectively, amonghypertensives. An interaction with hypertensive status was found for dietarylong-chain n–3 fatty acids (gday−1) and WFT decline (likelihood ratio test,P = 0.06). This exposure in plasmacholesteryl esters was also protective against WFT decline, particularlyamong hypertensives (OR = 0.51, P< 0.05).

One implication from our study is that diets rich in fatty acids of marineorigin should be considered for middle-aged hypertensive subjects. To thisend, randomised clinical trials are needed.