Seasonal variation influences fibromyalgia severity in terms of widespread pain among female patients: data from a large national registry

Introduction/objectives: Seasonal variation may influence musculoskeletal pain, and fibromyalgia is primarily characterized by widespread chronic pain. This study aimed to assess whether symptom severity in fibromyalgia varies by season. Methods: A retrospective, cross-sectional analysis was conducted on patients from the Italian Fibromyalgia Registry. Patients were grouped based on the season of their clinical evaluation. Disease severity was measured using disease-specific clinimetric tools: the Polysymptomatic Distress Scale (PSD), including the Widespread Pain Index (WPI) and Symptom Severity Scale (SSS), as well as the revised Fibromyalgia Impact Questionnaire (FIQR) and the modified Fibromyalgia Assessment Status (FASmod). Statistical analyses included the Kruskal-Wallis test and pairwise comparisons using the Dwass-Steel-Critchlow-Fligner test. Results: A total of 2614 patients were evaluated. Significant seasonal differences were found for both WPI (p = 0.042) and FASmod (p = 0.037). In female patients, these differences were more pronounced (WPI, p = 0.016; FASmod, p = 0.018), while no significant variation was observed in males. Pairwise analysis showed higher symptom severity in autumn compared to summer for both WPI (W = -4.009; p = 0.024) and FASmod (W = -3.800; p = 0.037). Conclusion: In fibromyalgia, widespread pain appears more severe in autumn than in summer, particularly among female patients. These findings highlight the potential role of seasonality in symptom modulation and underscore the importance of incorporating seasonal factors into patient management and education.