Causal effect of physical activity and sedentary behaviors on the risk of osteoarthritis: a univariate and multivariate Mendelian randomization study

There is still a lot of ambiguity about the link between physical activity (PA), sedentary behaviors (SBs) and osteoarthritis (OA). This study aimed to investigate the causal relationship of PA/SBs on the risk of OA. A univariate and multivariate Mendelian randomization (MR) analysis was conducted to investigate the causal effect of five PA phenotypes and three SB phenotypes on overall OA, knee OA, hip OA, total hip arthroplasty, and total knee arthroplasty (TKA). MR methods used were inverse-variance weighting, MR-Egger regressions, and weighted median. Sensitivity analysis examined horizontal pleiotropy and heterogeneity, and confirmed the reliability of the results. After false discovery rate, light do-it-yourself (DIY) activities decreased the risk for overall OA (OR: 0.32, 95% CI 0.16-0.65), and knee OA (OR: 0.26, 95% CI 0.12-0.51). Resulting in a decreased risk of walking for pleasure on overall OA (OR: 0.87, 95% CI 0.70-1.04) and knee OA (OR: 0.14, 95% CI 0.06-0.32) was also observed. Television viewing, however, significantly increased the risk of OA, knee OA, hip OA, and TKA. MVMR findings revealed independent causal impacts of walking for pleasure and watching television on overall and knee OA, taking into account BMI, smoking, and education. This study suggested that light DIY and walking for pleasure were beneficial for preventing OA, and the risk of OA and TKA increased with prolonged television watching.