The Association Between Central Obesity and Glenohumeral Joint Osteoarthritis and the Potential Mediating Role of Serum Triglycerides.

Background: The relationship between obesity and glenohumeral joint osteoarthritis (GJO) remains unclear, and the metabolic mechanisms involved are not well understood. This study investigated the prospective association between central obesity, assessed by waist-to-height ratio (WHtR), and GJO incidence, and examined whether triglycerides (TG) mediate this relationship.

Methods: We analyzed data from 32,881 UK Biobank participants enrolled between 2006 and 2014, with a median follow-up of 8.85 years (IQR: 7.15-10.75). Cox proportional hazards models and causal mediation analysis were used to estimate the direct and indirect effects of WHtR and TG on GJO risk, adjusting for demographic, socioeconomic, lifestyle, and comorbidity variables.

Results: Both WHtR and TG levels at baseline were significantly associated with higher GJO risk (p < 0.05). Compared to individuals with normal WHtR, those with severe central obesity had a 1.52-fold higher GJO risk (AHR = 1.52, 95% CI: 1.02-2.27, p = 0.038), independent of BMI. Similarly, participants in the highest TG tertile had a 1.46-fold increased risk compared to the lowest tertile (AHR = 1.46, 95% CI: 1.06-2.02, p = 0.022). These associations were consistent across subgroups by age, sex, physical activity, work intensity, and BMI. Mediation analysis showed that TG explained 21.9% of the WHtR-GJO association. The mediating effect was stronger in younger adults, women, and physically inactive individuals, but not significant in those with normal BMI or low physical workload.

Conclusions: Central obesity, as measured by WHtR, is an independent risk factor for GJO. TG partially mediates this association, suggesting that lipid toxicity may contribute to the metabolic pathogenesis of GJO.