Stair Climbing, Genetic Predisposition, and the Risk of Hip/Knee Osteoarthritis.

Background: Few studies have explored the association between stair climbing and osteoarthritis (OA) to determine whether the former is a protective or risk factor for the latter. This study prospectively evaluated the associations among stair climbing, genetic susceptibility, and their interaction with the risk of incident hip/knee OA.

Methods: The cohort analyses included 398 939 participants from the UK Biobank. Stair climbing was assessed using a questionnaire. Genetic risk scores consisting of 70, 83, and 87 single-nucleotide polymorphisms for hip, knee, and hip/knee OA were constructed. Cox proportional hazard regression models were used to estimate hazard ratios and 95% confidence intervals for the associations among stair climbing, genetic predisposition, and hip and/or knee OA risk.

Results: After 3 621 735 person-years of follow-up, 31 940 patients developed OA. Stair climbing was positively associated with incident hip/knee (p for trend < .001) and knee (p for trend < .0001) OA but not hip OA. After adjustments, compared with no stair climbing, climbing >150 steps/d was associated with a higher risk of hip/knee OA (hazard ratio, 1.08; 95% confidence interval: 1.03-1.12) and knee OA (hazard ratio, 1.13; 95% confidence interval, 1.06-1.20). Although no significant interaction between stair climbing and the genetic risk scores of OA risk was found, the above associations were only significant in participants with middle and high genetic risk scores.

Conclusions: A higher frequency of stair climbing was positively associated with the risk of knee OA but not hip OA, highlighting the importance of avoiding frequent stair climbing in preventing knee OA, especially in genetically predisposed individuals.