Association of sarcopenia and its prognostic value in symptomatic knee osteoarthritis among older people in China: the first longitudinal evidence from CHARLS

Abstract

Abstract Background The association between sarcopenia and knee osteoarthritis (KOA) among older people remains controversial. This study aimed to investigate the longitudinal association among the older Chinese population. Methods Data were attracted from 2 waves of the China Health and Retirement Longitudinal Study (CHARLS), and 6212 individuals aged ≥ 60 years were included. Sarcopenia status was defined by the Asian Working Group for Sarcopenia 2019 criteria. Multivariate logistic regression models were applied to estimate the impact of sarcopenia on KOA. A prognostic nomogram was developed through train-test cross-validation. Results At baseline in CHARLS 2015, the prevalence of symptomatic KOA in total populations, no-sarcopenia, possible sarcopenia and sarcopenia respondents were 12.7% (792/6212), 9% (270/2996), 17.5% (286/1638), and 15.0% (236/1578), respectively. Over a 3-year follow-up, a total of 4980 respondents were included. Compared to no-sarcopenia controls, Sarcopenia was associated with a significantly increased risk of new-onset KOA in the fully adjusted model (Odds ratio: 1.91, 95% confidence interval: 1.15–3.18), with incidence rates of 3.6% and 2.2% respectively. However, this association was non-significant for possible sarcopenia. Factors including sarcopenia status, age, gender, body mass index, self-reported health status, comorbidities, history of fall, and physical activities were used to construct the final prognostic model and nomogram, which indicated a considerable discrimination with area under receiver operating characteristic curve = 0.744 and C-index = 0.66. The calibration curve demonstrated significant agreement between predicted and actual observations. Decision curve analysis showed net benefits when clinical intervention was decided at a probability threshold from 1–17%. Conclusions Sarcopenia was associated with a higher incident risk of KOA, wherein muscle mass may play an important role. The inferior prognosis of sarcopenia in KOA needs more attention in clinical practice.