Effect of using repeated measurements of a Mediterranean style diet on the strength of the association with cardiovascular disease during 12 years: the Doetinchem Cohort Study

In cohort studies, often only one baseline measurement of dietary intake is available. This may underestimate the strength of the association with cardiovascular diseases (CVD). The main objective is to compare the strength of the association of a Mediterranean style diet with CVD using one baseline measurement of diet versus three repeated measurements over a 10-year period. We used dietary and lifestyle data of three rounds of the Doetinchem Cohort Study. At baseline, 7,769 persons aged 20-65 years were examined. Diet was assessed with a 178 item validated food-frequency questionnaire and operationalized with the Mediterranean Diet Score (MDS) ranging from 0 to 9. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95 % confidence intervals (CI). Analyses were adjusted for age, sex, and repeated measurements of smoking, sports, total energy intake, and educational level. Comparing an MDS of a parts per thousand yen5.5-9 to an MDS of 0-< 3.5, baseline MDS was associated with a 23 % lower risk [HR 0.77 (95 % CI 0.53-1.11)] and the updated mean with a 35 % lower risk [HR 0.65 (0.43-0.97)] of a composite of fatal CVD, nonfatal myocardial infarction, and stroke (composite CVD). For fatal CVD, baseline MDS was associated with a 13 % lower risk [HR 0.87 (0.36-2.07)] and the updated mean with a 56 % lower risk [HR 0.44 (0.19-1.05)]. The strength of the association between a Mediterranean style diet and CVD is likely underestimated because most studies so far used only one baseline measurement.