Higher estimated cardiorespiratory fitness levels were associated with lower risk of cardiometabolic multimorbidity: a retrospective cohort study from CHARLS.

BACKGROUND AND AIMS: Cardiometabolic multimorbidity (CMM) is significantly associated with an increased risk of all-cause mortality. However, evidence on the relationship between cardiorespiratory fitness (CRF) and CMM remains limited, particularly in Chinese populations. METHODS AND RESULTS: Data were derived from the China Health and Retirement Longitudinal Study. A total of 5,255 participants aged ≥45 years with up to 9 years of follow-up were included. Sex-specific body mass index (BMI)-based models were used to evaluate estimated CRF (eCRF). Skeletal muscle mass was assessed using appendicular skeletal muscle mass (ASM) and appendicular skeletal muscle mass index (ASMI). During the 9-year follow-up, 441 (8.4%) participants developed CMM. Kaplan-Meier survival analysis demonstrated that higher eCRF levels were associated with a lower cumulative risk of CMM. Multivariable Cox proportional hazards regression analysis revealed that after full adjustment for confounders, each 1-MET (1 mL kg-1·min-1) increase in eCRF was associated with an 18.9% (5.8%) reduction in the risk of CMM. In quartile analysis of eCRF, compared with the lowest quartile (Q1), the risk of CMM was 25.5% lower in Q2, 46.5% lower in Q3, and 61.0% lower in Q4. The fully adjusted RCS analysis indicated a linear relationship between eCRF and CMM risk. Mediation analysis suggested that skeletal muscle mass statistically mediated the association between eCRF and CMM, with mediated proportions of 22.69% for ASM and 40.54% for ASMI. CONCLUSION: Higher eCRF was associated with a reduced risk of CMM, and this association may be partially mediated by skeletal muscle mass.