Association between Mediterranean diet and Parkinson's disease in adults: A systematic review and meta-analysis of cohort studies

BACKGROUND: Parkinson's disease (PD) is a chronic neurodegenerative disorder, and previous studies have shown that the Mediterranean diet (MeDi) can be effective in reducing the incidence and progression of the disease. OBJECTIVE: The purpose of this study was to determine an association between adherence to MeDi and the risk of PD in adults by meta-analysis of cohort studies. METHODS: Online databases including Scopus, PubMed, Web of Science, and Google Scholar were searched up to March 2021. Cohort studies that examined the association of PD risk with adherence to MeDi were included. A pooled relative risk with a 95% confidence interval was calculated by a random effects meta-analysis. As well, bias assessment, assessment of heterogeneity, sensitivity, and subgroup analyses were carried out. The primary outcome was Parkinson's incidence. RESULTS: Overall four papers on PD risk were included in the present systematic review and meta-analysis. The effect size of the summary for the risk of overall PD, comparing the highest with the lowest adherence to MeDi, was 0.76 (95% CI: 0.59, 0.98), indicating a significant inverse association. CONCLUSIONS: Adherence to MeDi has a protective role against PD. Also, adhering to this dietary pattern at a younger age may be more beneficial in reducing the risk of PD. However, we suggest more prospective cohort studies in this regard.