Pos1425 Alimentation and Risk of Giant Cell Arteritis and Polymyalgia Rheumatica: Findings From the French E3n Cohort Study

Background: Giant cell arteritis (GCA), is frequently associated with polymyalgia rheumatica (PMR), suggesting a common pathophysiological mechanism. Their etiological mechanism remains unclear. The occurrence of GCA/PMR shows a geographical pattern, with higher rates observed in North regions. Additionally, individuals with African, Asian, or Hispanic ancestry tend to have a lower incidence of these conditions. These differences could be explained partially by environmental and lifestyle factors, such as diet. Objectives: The aim of this study was to assess the association between diet and the risk of developing GCA and/or PMR through a large prospective cohort. Methods: The E3N cohort study (Etude Epidémiologique Auprès des Femmes de la Mutuelle Générale de l'éducation nationale) is a large prospective cohort study, conducted in France that has included 98,995 women since 1990. Cases of GCA/PMR were identified with an algorithm combining self-reported diagnoses and a glucocorticoid reimbursement 1. Dietary information was collected in 1993 through a validated food frequency questionnaire. Diet was analyzed using three approaches: food groups, dietary patterns via factor analysis, and the adherence to the Mediterranean Diet Score, using a 9-unit dietary score. Hazard ratios (HRs) and 95% confidence interval (95% CIs) for incident GCA and/or PMR were estimated using Cox proportional hazards regression models adjusted for age and the main potential confounders. Results: Among 64,296 women, we identified 678 GCA/PMR cases, including 139 GCA, 278 PMR (261 could not be differenciated). The mean time between diet Pattern assessment and occurrence of GCA/PMR was 19.6 ± 7.6 years. Mediterranean diet adherence score was not associated with occurrence of GCA/PMR (aHR 1.01 for high versus low adherence; 95% CI 0.83–1.24; P for trend >0.05) nor GCA (aHR 1.04; 95% CI 0.67–1.63), or PMR (aHR 0.81; 95%CI 0.58–1.13). Conversely, a Western diet was associated with an increased risk in GCA/PMR (aHR 95%CI 1.40 for 4th quartile versus 1st quartile; 95%CI 1.07–1.85; P for trend = 0.01). The risk remained significant among PMR cases analyzed separately (aHR 1.52; 95%CI 1.00 – 2.32; P for trend = 0.04), but not with GCA cases (aHR 1.09; 95% CI 0.58–2.03; P for trend = 0.67) (Table 1). Conclusion: We found a positive association between Western diet and the risk of GCA/PMR occurrence, mainly at the expense of PMR cases. This diet is characterized by high consumption of saturated fats, carbohydrates, salt and cholesterol, and low consumption of fiber, vitamins, and minerals. It is associated with chronic inflammatory state, at the origin of tissue inflammation, which has already been linked to a wide range of chronic diseases (cardiovascular disease, cancer, etc.). The pathophysiology of PMR, involving high concentrations of pro-inflammatory cytokines in the affected joints and muscles, could therefore be partly mediated by this chronic inflammatory state linked to the Western diet. REFERENCES: 1 Barde F, Ascione S, Pacoureau L, et al. Accuracy of self-reported diagnoses of polymyalgia rheumatica and giant cell arteritis in the French prospective E3N- EPIC cohort: A validation study. Semin Arthritis Rheum. 2024;64:152298. Table 1. Hazards ratios for GCA and/or PMR according to quartiles of dietary patterns in the study population Acknowledgements: The present work was conducted thanks to a donation from SANOFI. Disclosure of Interests: None declared.