Does smoking reduce the progression of osteoarthritis? Meta-analysis of observational studies

OBJECTIVE: To determine whether smoking reduces the progression of osteoarthritis (OA). METHODS: Observational studies examining smoking and progression of OA were systematically searched through Medline (1948-), EMBase (1980-), Web of Science, PubMed, and Google and relevant references. The search was last updated in May 2012. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were directly retrieved or calculated. Current standards for reporting meta-analyses of observational studies (Meta-Analysis of Observational Studies in Epidemiology) were followed. Quality-related aspects such as study design, setting, sample selection, definition of progression, and confounding bias were recorded. Stratified and meta-regression analyses were undertaken to examine the covariates. RESULTS: Sixteen studies (976,564 participants) were identified from the literature. Overall, there was no significant association between smoking and progression of OA (OR 0.92; 95% CI 0.83, 1.02). There was moderate heterogeneity of results (I(2) = 57.3%, P = 0.0024). Subgroup analyses showed some associations of marginal significance; however, meta-regression did not confirm any significant results. CONCLUSION: There is no compelling evidence that smoking has a protective effect on the progression of OA. The results concur with a previous meta-analysis published by this group that showed no association between smoking and incidence of OA. Taken together, smoking does not appear to reduce either the incidence or progression of OA.