Higher body mass index increases the risk of shoulder adhesive capsulitis in young adults: a nationwide cohort study

Background: The impact of overweight on the incidence of shoulder adhesive capsulitis (AC) has not been clearly proven. This study aimed to investigate the association between overweight and AC by age using a large-scale nationwide population-based cohort in Korea. Methods: We analyzed clinical data from 3,517,066 individuals older than 20 years who had undergone a National Health Insurance Service health checkup in 2009. Patients who visited a hospital or private clinic to treat shoulder pain at least three times in 1 year and were assigned a diagnostic code for AC (International Classification of Diseases,10th Revision code M75.00) were identified using claims data during a median follow-up duration of 8.3 years. Hazard ratios (HRs) and 95% confidence intervals for AC were calculated using the Cox proportional hazards model. Results: The adjusted HR for AC in the < 40 year group started to increase in overweight status and was associated with the severity of obesity (body mass index (BMI) < 18.5; 0.654 (0.613-0.697), <23; 1, <25; 1.272 (1.231-1.315), <30; 1.322 (1.281-1.364), ≥30; 1.332 (1.253-1.416)). But in the 40-64 year group and the ≥ 65 year group, there was no significant increasing trend of HR for AC according to BMI level. We conducted a subgroup analysis based on the BMI 23 for defining overweight and presence of comorbidities including diabetes and hyperlipidemia. The adjusted HR for AC was highest with overweight and comorbidities of diabetes and hyperlipidemia (diabetes; 1.528 (1.508-1.549), hyperlipidemia; 1.212 (1.199-1.226)). Conclusions: In the young age group (20-40 years), a higher BMI level increased the HR for AC. Overweight along with diabetes or hyperlipidemia significantly increased the risk of AC.