Individuals With Multijoint Osteoarthritis Demonstrate Larger Longitudinal Declines in Frailty: Data From the Canadian Longitudinal Study on Aging

OBJECTIVE: The aim of this study was to test the hypothesis that multijoint osteoarthritis would modify the relation between time and frailty progression, in which more affected joints would lead to larger declines over six years compared to those without osteoarthritis using data from the Canadian Longitudinal Study on Aging. METHODS: Frailty was quantified using a frailty index at baseline, three-year, and six-year follow-up. Osteoarthritis was self-reported physician diagnosis of knee, hip, or hand. Participants were categorized as having none, one, two, or three affected joints at baseline. Linear mixed-effects models adjusted for age, body mass index, marital status, sitting time, light-moderate physical activity, strenuous physical activity, and sex were performed to test the interaction between time and multijoint osteoarthritis on frailty trajectories over six years. RESULTS: A total of 13,757 participants were included (mean frailty: 0.16 ± 0.05); 10,193 had no osteoarthritis, 2,535 had one affected joint, 806 had two affected joints, and 223 had three affected joints. Individuals without osteoarthritis had the lowest baseline frailty, followed stepwise by the one-joint group, two-joint group, and three-joint group (P < 0.001). Baseline multijoint osteoarthritis was positively associated with frailty progression over six years (β = 0.105, 95% confidence interval [CI] 0.027-0.170). Frailty slopes across groups were the following: no osteoarthritis (β = 0.237, 95% CI 0.225-0.247), one-joint group (β = 0.293, 95% CI 0.262-0.310), two-joint group (β = 0.348, 95% CI 0.327-0.368), and three-joint group (β = 0.330, 95% CI 0.291-0.371). Frailty progressed faster in multijoint group (at least two joints) versus single-joint osteoarthritis (β = 0.070, 95% CI 0.029-0.109). CONCLUSION: Individuals with osteoarthritis affecting two or three joints experienced a 40% to 47% faster rate of frailty progression compared with those without osteoarthritis despite starting at a higher baseline frailty, highlighting multijoint involvement as a marker of heightened risk of accumulating health deficits.