Associations of dietary diversity score, dietary diversity of protein index, and lifelines diet score with Parkinson’s disease: a case-control study

Parkinson’s disease is a progressive neurodegenerative disorder with both motor and non-motor manifestations. Dietary factors, including dietary diversity, protein source variety, and adherence to healthy eating patterns, may impact Parkinson’s disease risk. The goal of the current case-control research was to examine the links between the Dietary Diversity Score (DDS), the Diversity of Dietary Protein Index (DDPI), and the Lifeline Diet Score (LLDS) with the odds of Parkinson’s disease among an Iranian population. A total of 320 individuals (215 controls and 105 newly diagnosed Parkinson’s disease patients) were recruited in Arak, Iran. Dietary intake was evaluated by applying a validated 147-item food frequency questionnaire, and DDS, DDPI, and LLDS were calculated. Multivariate logistic regression was utilized to estimate odds ratios (ORs) and 95% confidence intervals (CIs), adjusting for major confounders. Greater DDS and LLDS were strongly linked to reduced odds of Parkinson’s disease (Adjusted OR for DDS = 0.287, 95% CI: 0.185–0.447; Adjusted OR for LLDS = 0.879, 95% CI: 0.803–0.963). However, DDPI showed no significant association with Parkinson’s disease after adjustment. Higher dietary diversity and greater adherence to a high-quality dietary pattern were associated with lower odds of Parkinson’s disease, whereas no significant association was observed for protein source diversity. Given the case-control design, these findings should be interpreted as associations rather than evidence of causality.