Socioeconomic status modifies the association between adherence to the Mediterranean diet and cognitive outcomes: results from the Collaborative PROMED-COG Pooled Cohorts Study

Background: This study examines whether adherence to the Mediterranean diet (MD), alone and combined with physical activity (MedEx), is associated with cognitive decline and dementia incidence, with socioeconomic status (SES) as a potential modifier. Methods: We included 8,568 subjects (mean age 72.3 ± 9.6 years, 52.4% female) from three pooled Italian population-based studies. MD adherence was assessed using the Panagiotakos algorithm. We analyzed the association of MD and MedEx adherence, both continuously and categorized in tertiles, with cognitive decline and incident dementia using Cox regression. SES modification was examined through interaction analysis and SES-stratified models. Results: Cognitive decline occurred in 38.1% of participants but was not associated with MD adherence. In SES-stratified analysis, among high SES individuals, each 2-point increase in MD adherence reduced cognitive decline risk by 14%, and high MD adherence was associated with a 48% reduction (HR 0.52, 95%CI 0.31–0.90). In this group, medium MedEx adherence reduced cognitive decline risk by 77% (HR 0.23, 95%CI 0.07–0.83). No significant association was found between MD/MedEx adherence and incident dementia (4.2%), regardless of SES. Discussion: SES may modify the relationship between MD and cognitive decline, with greater benefits observed in higher SES groups. Further studies, particularly in vulnerable populations, are needed to inform tailored preventive strategies for cognitive decline.