Association between digestive diseases and symptomatic knee osteoarthritis in Chinese participants: a prospective cohort study

BACKGROUND: Digestive diseases and symptomatic knee osteoarthritis (OA) frequently occur in older adults, yet prospective evidence clarifying their temporal relationship remains limited, particularly in Asian populations. This study examined the relationship between digestive diseases and the risk of incident symptomatic knee OA in a nationally representative cohort of middle‑aged and older Chinese adults. METHODS: Data were obtained from the China Health and Retirement Longitudinal Study (CHARLS) from 2011 to 2018. A total of 6,281 adults without symptomatic knee OA at baseline were included. Digestive diseases were defined as exposure, and incident symptomatic knee osteoarthritis was the outcome of interest. Kaplan-Meier survival curves with log‑rank tests were used to compare cumulative incidence, and multivariable Cox proportional hazards models were applied to estimate hazard ratios. Sensitivity analyses included propensity score matching (PSM), prespecified subgroup analyses presented as forest plots, and E-value calculations. RESULTS: A total of 6,281 participants were included in the analytical cohort (mean age, 58.6 ± 8.8 years; 53.5% women), with a median follow‑up of 84 months. Over the observation period, participants reporting digestive diseases experienced a markedly higher cumulative incidence of symptomatic knee OA compared with those without digestive conditions (31.4% versus 20.9%; log‑rank p < 0.01). After adjustment for potential confounders, multivariable Cox models indicated a higher risk of symptomatic knee OA among participants with digestive diseases (adjusted HR = 1.40; 95% CI: 1.25-1.57; p < 0.001). Similar effect estimates were obtained in the PSM (HR = 1.42; 95% CI: 1.23-1.64; p < 0.001). Subgroup analyses showed similar associations, with no statistically significant interactions detected. E‑value was 2.17. CONCLUSION: Digestive diseases are linked to a higher likelihood of symptomatic knee OA in this prospective cohort, supporting a temporal relationship between digestive disorders and the development of symptomatic knee OA.