The Mediating Role of Functional Limitations Between Recurrent Falls and Knee Osteoarthritis: An Observational Study Based on CHARLS 2015

Summary

This cross-sectional observational mediation analysis suggests that functional limitations partially mediate the association between recurrent falls and knee osteoarthritis, highlighting the importance of fall prevention and functional maintenance in middle-aged and older adults.

Abstract

Studies on the relationships among functional limitations, recurrent falls, and knee osteoarthritis remain limited. This cross-sectional observational study examined the associations among recurrent falls, functional limitations, and knee osteoarthritis and evaluated whether functional limitations mediated the relationship between recurrent falls and knee osteoarthritis. After excluding participants younger than 45 years and those with missing data for core variables and covariates, 2,278 participants from the CHARLS 2015 survey were included in complete-case analysis. Spearman correlation analysis was used to assess the correlations among recurrent falls, functional limitation score, and knee osteoarthritis. Because knee osteoarthritis was treated as a binary outcome, multivariable logistic regression was used to evaluate its association with recurrent falls. Mediation analysis was performed within a bootstrap mediation framework based on a linear mediator model and a logistic outcome model, with recurrent falls as the independent variable, functional limitation score as the mediator, and knee osteoarthritis as the dependent variable. Recurrent falls were significantly associated with higher odds of knee osteoarthritis in the adjusted model. After the functional limitation score was added to the model, recurrent falls remained significantly associated with knee osteoarthritis, and the functional limitation score was also significantly associated with knee osteoarthritis. Bootstrap mediation analysis showed a total effect of 0.093 (95% CI: 0.050–0.138), a direct effect of 0.079 (95% CI: 0.037–0.123), and an indirect effect through functional limitations of 0.014 (95% CI: 0.006–0.023), accounting for 14.92% of the total effect. These findings support a statistically significant mediation pattern in which functional limitations serve as an intermediate factor in the association between recurrent falls and knee osteoarthritis. These results highlight the importance of integrating fall-risk assessment and functional status evaluation into health management for knee osteoarthritis in middle-aged and older adults.

Introduction

Knee osteoarthritis (KOA) is a common degenerative joint disease that usually manifests as knee pain, limited mobility, and joint stiffness^1,2,3. With the prolonged course of the disease, patients often experience dysfunction of the knee joint, and in severe cases, they even lose the ability to perform daily activities^4,5. Knee osteoarthritis has a high epidemiologic burden worldwide, and it is especially common in the elderly population^6,7,

Protocol

Data
The CHARLS database is based on a survey of health, economic, and social activities in China³³. All the CHARLSs received ethical approval from the Institutional Review Board (IRB) of Peking University. The IRB approval number for the main household survey (including anthropometrics) was IRB0000105211015. In the current study, the authors applied the 2015 survey. The sample consisted of 21,095 participants. Participants aged ≤45 years or with missing age information were excluded. Participants with missing data for the three core variables, recurrent falls, functional limitation score, and knee osteoarthritis, w....

Results

Characteristics of participants
The study population was selected through the screening process shown in Figure 1. A total of 21,095 participants from the CHARLS 2015 survey were initially screened. After excluding 1,934 participants aged ≤45 years or with missing age information, 19,161 participants remained. Among them, 6,572 participants were excluded due to missing data on recurrent falls, functional limitation score, or knee osteoarthritis, and 10,311 were further e.......

Discussion

This study examined the mediating role of functional limitations in the association between recurrent falls and knee osteoarthritis among middle-aged and older Chinese adults. The results showed that recurrent falls were associated with knee osteoarthritis and that functional limitations partially mediated this association. These findings indicate that functional decline is not only a consequence accompanying falls or knee symptoms, but also an important intermediate state linking fall history with knee osteoarthritis-re.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
China Health and Retirement Longitudinal Study 2015 survey data	China Health and Retirement Longitudinal Study, Peking University	Not applicable	Publicly available survey dataset used for the secondary analysis. Registered researchers can access the data through the CHARLS official website.
Dplyr R Package	CRAN	Version 1.1.4	Used for data cleaning, filtering, recoding, and variable construction.
Ggplot2 R Package	CRAN	Version 3.4.4	Used for visualization and figure preparation.
Mediation R Package	CRAN	Version 4.5.1	Used to perform bootstrap mediation analysis based on a linear mediator model and logistic outcome model.
Psych R Package	CRAN	Version 2.5.6	Used for descriptive statistics and scale-related data handling.
R software	R Foundation for Statistical Computing	Version 4.4.1	Used for data processing, variable construction, statistical analysis, regression modeling, mediation analysis, and figure/table generation.
Tableone R Package	CRAN	Version 0.13.2	Used to summarize baseline characteristics of the study population.
Tidyverse R Package	CRAN	Version 2.0.0	Used for data organization and data management.