AB1641 TOBACCO SMOKING HAS A PREVENTIVE EFFECT ON THE INCIDENCE OF KNEE OSTEOARTHRITIS: 10-YEAR RETROSPECTIVE COHORT STUDY BASED ON KOREA NATIONAL HEALTH INSURANCE SERVICE-HEALTH SCREENING DATABASE

Abstract

BackgroundPrevious cross-sectional studies reported that smoking lowers the incidence of knee osteoarthritis, however, some studies show no correlation between smoking and knee osteoarthritis. Thus the relationship between the two has not been clarified [1,2]. To address this issue, we designed a retrospective cohort study to investigate the association between smoking and knee osteoarthritis, using a large-scale claim database from Korea. To the best of our knowledge, this is the first retrospective cohort study on smoking and knee osteoarthritis in Korea.ObjectivesWe intended to investigate whether there was a difference in the incidence of knee osteoarthritis between patients with a history of current smoking, past smoking and those without a history of smoking.MethodsThe Korea National Health Insurance Service-Health Screening database is registered with 98% of Koreans and includes all insurance claims. From this database, a retrospective cohort observational study was conducted on 316,387 adults who had undergone the national health examination. Patients diagnosed with knee osteoarthritis prior to the examination and patients who were diagnosed with knee osteoarthritis in 2002 were excluded. The primary endpoint of this study was a diagnosis of knee osteoarthritis. The operational definition of diagnosis of knee osteoarthritis was knee osteoarthritis code (M17) or any site of osteoarthritis code (M15 to M19) along with a knee x-ray (G720, G721) [3]. The study population was followed from the day of health screening at index year to the date of incidence of knee osteoarthritis, the date of death, or December 31, 2019, whichever comes first.ResultsThe patient group was classified into non-smoker, ex-smoker, and smoker groups according to the responses to the health examination questionnaire. The baseline characteristics of each group are included in Table 1. The incidence of knee osteoarthritis was 38.9%, 26%, and 23% in each group of non-smoker, ex-smoker, and smoker group with statistical significance (P-value < 0.001). When the disease-free probability for knee osteoarthritis was presented using the Kaplan-Meier curve, it was confirmed that the risk of osteoarthritis incidence was significantly different between the non-smoker group and the smoker group as time passes (Figure 1, P-value for Log-rank test < 0.001). The hazard ratio and 95% confidence intervals of ex-smoker to non-smoker were 0.95 (0.83-0.97), and those of smoker to non-smoker were 0.89 (0.87-0.91).ConclusionThis large-scale retrospective cohort study showed a low incidence of knee osteoarthritis in smokers and ex-smokers during a follow-up period when compared to non-smokers in Korea. Additional studies on the relationship between smoking and knee osteoarthritis are required in the future.