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.