Exploring the Relationship Between Physical Activity and Multimorbidity: Insights from the CHARLS Database

Background Physical activity has been widely recognized for its important role in preventing cardiovascular and other chronic diseases. However, the specific relationship between different levels of physical activity and various chronic diseases, including multimorbidity, remains unclear, which require further investigation. Methods This study utilized the China Health and Retirement Longitudinal Study (CHARLS) database to classify physical activity levels based on metabolic equivalents (MET). The analysis focused on the relationship between low, moderate, and high physical activity levels and various chronic diseases, as well as the co-occurrence of multiple diseases. Multivariable logistic regression models were employed to assess the association between different activity levels and the risk of chronic diseases, while stratified analyses explored the impact of demographic factors on these associations. Additionally, a restricted cubic spline (RCS) model was applied to investigate potential nonlinear relationships between total MET and chronic disease risks. Results The results showed that compared to low activity levels, moderate and high levels of physical activity significantly reduced the risk of cardiovascular diseases and respiratory diseases, with a nonlinear dose-response relationship. High levels of physical activity also significantly lowered the risk of multimorbidity, particularly the coexistence of three or more chronic diseases (OR = 0.55, 95% CI: 0.47, 0.65, P < 0.01). However, moderate activity levels were associated with increased risks of dyslipidemia and diabetes, while high levels of activity were linked to higher risks of arthritis and kidney diseases. Stratified analyses revealed that demographic factors influenced the association between physical activity and disease risk. Conclusion Moderate and high levels of physical activity provide significant protection against cardiovascular and respiratory diseases and effectively reduce the risk of multimorbidity. However, the increased risk of certain metabolic and joint diseases with higher activity levels warrants further attention. Future research should clarify the impact of physical activity on different populations and chronic diseases, with randomized controlled trials needed to verify causality.