Inflammation and bone: Geelong osteoporosis study

Objectives: Osteoporosis is a disease state possibly underpinned by systemic inflammation. Thus, we aimed to determine whether serum interleukin 6 (IL-6), a marker of systemic inflammation, is associated with BMD in a population-based sample of men. Methods: This cross-sectional study utilised data from 1143 men aged 20-96 y (median 61.5, IQR 44.5-75.5) participating in the Geelong Osteoporosis Study. Serum IL-6 was measured following an overnight fast using ELISA (R&D Systems). BMD (g/cm2) was measured at the PA-spine, femoral neck, total body and forearm using DXA (Lunar). Anthropometric measurements and socioeconomic status (SES) were determined and information on medication use and lifestyle was obtained via questionnaire. IL-6 values were natural log transformed (ln-IL6) and associations between ln-IL6 and BMD were tested using Pearson’s correlation. Multivariable regression models were developed to test the association between ln-IL-6 and BMD after adjusting for age and weight. Results: Ln-IL-6 (median 1.9 mg/ml, IQR 1.2-3.2) was positively correlated with age (r=0.52, p<0.001) and negatively with BMD at the femoral neck (r=-0.27, p<0.001), total body (r=-0.16, p<0.001), distal-forearm (r=-0.17, p<0.001) and mid forearm (r=-0.19, p<0.001) sites. After adjustments, ln-IL-6 was associated with decreased BMD at the femoral neck (β -0.014, se±0.006, p=0.015), total body (β -0.010±0.004, p=0.010), distal (β -0.010±0.003, p=0.050) and mid forearm (β -0.009±0.003, p=0.011), but not spine BMD (β -0.010±0.010, p=0.237). These associations persisted after further adjustment for smoking, physical activity, SES, alcohol consumption, medications (statins, antidepressants, nonsteroidal anti-inflammatory drugs) and arthritis. Conclusion: These population-based data suggests IL-6 is independently associated with BMD in adult men. This supports an aetiological role for inflammatory activity in the pathophysiology of osteoporosis, suggesting a possible target for therapy.