Leptin levels are associated with radiographic knee osteoarthritis among a cohort of mid-life women

OBJECTIVE: To relate serum leptin levels to prevalent and incident radiographic knee osteoarthritis (OAK) and to determine if patterns of change in longitudinal serum leptin measures differ by knee OA status over a 10-year period. METHODS: Participants in the Michigan Study of Women's Health Across the Nation underwent bilateral knee radiographs at baseline and follow-up visits 2, 4 and 11 for ascertainment of OAK status (Kellgren-Lawrence score >/= 2). Serum leptin measures were available from baseline, follow-up visits 1 and 3-7. RESULTS: The baseline prevalence of OAK (average age 46 years) was 18%; the two-year incidence of OAK at follow-up visits 2 and 4 was 18% and 14%, respectively. Serum leptin levels were associated with prevalent and incident OAK. A 5 ng/mL increase in serum leptin was associated with 38% higher odds of prevalent OAK (OR=1.38, 95% CI 1.26, 1.52) and with 31% greater odds of incident OAK (OR=1.31, 95% CI 1.21, 1.41) after adjustment for covariates including BMI residuals. Leptin levels increased with time; on average, serum leptin levels increased by 0.38 ng/mL per year (p=0.0004). Women with incident OAK during the 10-year follow-up had consistently higher serum leptin levels as compared to women with no OAK during follow-up. CONCLUSIONS: Our findings support a metabolic role of obesity on knee OA. Better understanding of the mechanisms by which increased fat mass is associated with joint damage is needed. Management of cardiometabolic dysfunction, including elevated serum leptin levels may be beneficial in forestalling the onset or progression of knee OA. (c) 2012 by the American College of Rheumatology.