Reproductive, Dietary, and Physical Activity Factors Associated With Multiple Sclerosis: A Case–Control Study

ABSTRACT Background and Aims Multiple sclerosis (MS) is a chronic inflammatory disease influenced by genetic and environmental factors. Dietary habits, reproductive characteristics, and physical activity have been proposed as potential contributors to MS susceptibility. This study aimed to investigate the association of dietary intake, supplement use, reproductive factors, and physical activity with MS in Kermanshah Province, Iran. Methods This case–control study included 600 participants (300 MS patients and 300 matched healthy controls) from Kermanshah. Data were collected using the validated Persian version of the Environmental Exposure and Lifestyle Risk Factors in MS Questionnaire (EnvIMS‐Q). Logistic regression analyses were performed to estimate crude and adjusted odds ratios (ORs) with 95% confidence intervals (CIs). Results Compared with controls, participants with MS reported lower consumption of several foods, including fish (adjusted OR = 0.31, 95% CI 0.19–0.50), seafood (adjusted OR = 0.31, 95% CI 0.10–0.98), nuts (adjusted OR = 0.60, 95% CI 0.39–0.93), and dairy products. Fish oil supplementation was less common among patients with MS (adjusted OR = 0.28, 95% CI 0.13–0.61). Female patients reported higher frequencies of oral contraceptive use, miscarriage, and assisted reproduction. Vigorous physical activity was significantly lower among patients than controls, whereas mild physical activity did not differ significantly. No significant association was observed for vitamin D supplementation. Conclusion This study identified associations between several dietary, reproductive, and lifestyle factors and MS in a high‐prevalence region of Iran. Lower consumption of selected nutrient‐rich foods, lower fish oil supplement use, certain reproductive factors, and lower levels of vigorous physical activity were associated with higher odds of MS. Prospective studies are needed to clarify temporal relationships and causality.