Introduction: Low socioeconomic status is associated with poor health outcomes and unhealthy behaviors. The traditional Mediterranean diet (MD) has been related to reduced risk of major chronic diseases and mortality and exhibits a socioeconomic gradient.
Hypothesis: The association of the MD with cardiovascular risk (CVD) may differ across different socioeconomic status groups.
Methods: Population-based cohort study on 18,710 individuals apparently free at enrollment from CVD and diabetes, randomly recruited from the general population of the MOLI-SANI study (Italy). The cohort was followed up for a median of 4.3 years (81,367 person-years). Food intake was recorded by the EPIC food frequency questionnaire. Adherence to the MD was appraised by the Greek Mediterranean diet score. Household income (Euros/year) and educational levels were used as socioeconomic status indicators. Incident CVD events were identified from the hospital discharge records based on ICD-9 codes.
Results: We identified 252 CVD events (CHD n=207, stroke n=45). A 2-point increase in the MD score was associated with 16% reduced risk (2% to 28%). The protective effect of the MD differed across educational levels and household income categories (p for interaction=0.042 and 0.0081 respectively) with subjects in the highest category of either education or income reporting a significant reduction of CVD risk in respect to the lowest (HR=0.40;0.23-0.69 and HR=0.38; 0.22-0.64 respectively). In multivariable analysis further controlled for adherence to the MD, nutrient intake varied across socioeconomic strata with those with higher status reporting higher intake of antioxidants and polyphenols (see Table).
Conclusions: The protective effect of the MD on CVD risk was only evident within high socioeconomic status groups. At comparable levels of adherence to the MD, differences in dietary antioxidant and polyphenol intakes were apparent across population strata. These nutritional gaps may partly explain the observed socioeconomic pattern of protection.