High adherence to the Mediterranean diet is associated with cardiovascular protection in higher but not in lower socioeconomic groups: prospective findings from the Moli-sani study

Background: It is uncertain whether the cardiovascular benefits associated with Mediterranean diet (MD) may differ across socioeconomic groups. Methods: Prospective analysis on 18991 men and women aged ≥35 years from the general population of the Moli-sani cohort (Italy). Adherence to MD was appraised by the Mediterranean diet score (MDS). Household income (euros/year) and educational level were used as indicators of socioeconomic status. Hazard ratios (HR) were calculated by multivariable Cox proportional hazard models. Results: Over 4.3 years of follow-up, 252 cardiovascular disease (CVD) events occurred. Overall, a two-point increase in MDS was associated with 15% reduced CVD risk (95% confidence interval: 1% to 27%). Such association was evident in highly (HR = 0.43; 0.25-0.72) but not in less (HR = 0.94; 0.78-1.14) educated subjects (P for interaction = 0.042). Similarly, CVD advantages associated with the MD were confined to the high household income group (HR = 0.39; 0.23-0.66, and HR = 1.01; 0.79-1.29 for high- and low-income groups, respectively; P for interaction = 0.0098). In a subgroup of individuals of different socioeconomic status but sharing similar MDS, diet-related disparities were found as different intakes of antioxidants and polyphenols, fatty acids, micronutrients, dietary antioxidant capacity, dietary diversity, organic vegetables and whole grain bread consumption. Conclusions: MD is associated with lower CVD risk but this relationship is confined to higher socioeconomic groups. In groups sharing similar scores of adherence to MD, diet-related disparities across socioeconomic groups persisted. These nutritional gaps may reasonably explain at least in part the socioeconomic pattern of CVD protection from the MD.