Association between direct and indirect smoking and osteoarthritis prevalence in Koreans: a cross-sectional study

OBJECTIVES: To assess the association between smoking patterns and knee and hip joint osteoarthritis (OA) prevalence in Koreans aged 50 years or older with focus on knee OA. DESIGN: Cross-sectional study using nationally representative data. SETTING: Data were collected at portable Health Examination Centres in Korea. PARTICIPANTS: Data of 9064 participants of the 5th Korean National Health and Nutrition Examination Survey (2010–2012) aged 50 years or older who received knee or hip joint X-rays out of 31 596 total surveyees were analysed. PRIMARY OUTCOME MEASURES: OA prevalence by smoking behaviour (current smoking, past smoking, indirect smoking and non-smoking). SECONDARY OUTCOME MEASURES: Estimated risk of OA by smoking amount, period, pack-years and indirect smoking exposure time to assess the association between smoking-related factors and knee OA by calculating ORs and adjusting for covariates in a complex sampling design. A multinomial logistic regression analysis and backward elimination method was used. RESULTS: OA prevalence in Koreans aged 50 years or older was 13.9%, with prevalence about 3.5 times higher in women (men 5.7%, women 20.1%). ORs for knee and hip joint OA prevalence by smoking behaviour in male indirect-smokers were lower than those in non-smokers in age and sex (OR 0.271; 95% CI 0.088 to 0.828), and selective adjustments (OR 0.314; 95% CI 0.102 to 0.966). All other analyses for smoking behaviour and total OA prevalence, and knee OA prevalence were not significantly different. Associations between smoking amount, period, pack-years and knee OA prevalence were non-significant in ever-smokers. Associations between indirect smoking exposure time and knee OA prevalence were also non-significant. CONCLUSIONS: This study found that though direct and previous smoking and OA prevalence were not associated, there was a weak relationship between indirect smoking and OA.