Investigation of the Associations of Smoking With Hip Osteoarthritis: A Baseline Cross-Sectional and Four- to Five-Year Longitudinal Multicohort Study

Objective: This study aimed to investigate the effect of smoking on the prevalence, incidence, and progression of hip osteoarthritis (OA). We used data from the Osteoarthritis Initiative (OAI) and the Cohort Hip and Cohort Knee (CHECK) studies. Methods: We analyzed 9,386 hips from 4,716 participants (OAI cohort) and 1,954 hips from 977 participants (CHECK cohort). The primary exposure was smoking status at baseline, categorized as current, former, or never smoker. Outcomes of radiographic hip OA (RHOA) and symptomatic hip OA were evaluated both cross-sectionally at baseline and longitudinally over a 4- to 5-year follow-up, with adjustments for major covariates. Results: No significant differences were observed between current or former smokers and never smokers for any of the outcomes examined, either at baseline or at the 4- to 5-year follow-up. In the cross-sectional analysis, the odds ratios with 95% confidence intervals for the prevalence of RHOA for current and former smokers were 1.29 (0.68–2.46) and 0.99 (0.70–1.40) in the OAI cohort and 1.38 (0.78–2.44) and 0.85 (0.54–1.32) in the CHECK cohort, respectively. In the longitudinal analysis, odds ratio with 95% confidence intervals for the incidence of RHOA were 1.03 (0.23–4.50) and 0.92 (0.46–1.85) in the OAI cohort and 0.61 (0.34–1.11) and 1.00 (0.69–1.44) in the CHECK cohort, respectively. Conclusion: Our study found no clear association between smoking and the prevalence, incidence, or progression of RHOA or symptomatic hip OA, either at baseline or over a 4- to 5-year period.