Objective To assess the associations of smoking, body weight and physical activity with the risk of undergoing total joint replacement (TJR) in a population-based cohort of men.
Methods A cohort study of 11 388 men that integrated clinical data with hospital morbidity data and mortality records. In three separate age groups we modelled the risk of TJR on weight, height, co-morbidity, injury, socioeconomic status, years of smoking and exercise, using Cox proportional hazards regressions and competing risk regressions.
Results A dose-response relationship between both weight and smoking, and risk of TJR was observed. Being overweight independently increased the risk of TJR, while smoking lowered the risk. The decreased risk among smokers was demonstrated in both Cox and CRR models and it became apparent after 23 years of exposure. Men who were in the highest quartile (48+ years of smoking) were 44%–52% less likely to undergo TJR than never-smokers. Tests for trend in the log HRs across both smoking and weight quantiles yielded p<0.001. Vigorous exercise increased the hazard of TJR, however, the association reached statistical significance only in the 70–74 year-old age-group (adjusted-hazard ratio: 1.71, 95% CI 1.26 to 2.33). Adjusting for Deyo–Charlson Index or Elixhauser's co-morbidities did not eliminate these associations.
Conclusion Being overweight and reporting vigorous physical activity increased the risk of TJR. This study is the first to demonstrate a strong inverse dose-response effect of duration of smoking and TJR. More research is needed to better understand the role of smoking in the pathogenesis of osteoarthritis.