Cardiorespiratory Fitness, Multimorbidity Risk, and 15-Year Trajectories in Chronic Disease Accumulation: A Prospective Longitudinal Study

BACKGROUND: Cardiorespiratory fitness (CRF) has been linked to lower risk of individual chronic diseases, but little is known about the CRF in relation to multimorbidity. OBJECTIVES: The authors investigated the association between CRF and multimorbidity risk and explored differences in the trajectories of chronic disease accumulation at varying levels of CRF. METHODS: The study included 38,348 adults from the UK Biobank (mean age 55.21 ± 8.15 years; 51.95% female) who were followed for up to 15 years to detect the incidence of 59 common chronic diseases. CRF was estimated using a 6-minute submaximal exercise test and tertiled as low, moderate, and high (after standardization by age and sex). Multimorbidity was defined as the presence of 2 or more chronic diseases. Data were analyzed using Cox regression, Laplace regression, and linear mixed-effects models. RESULTS: During the follow-up (median [IQR]: 11.57 [7.39-11.76] years), 15,368 (40.08%) participants developed multimorbidity. The risk of multimorbidity was 21% lower in participants with high compared to low CRF (HR: 0.79 [95% CI: 0.76-0.83]). The median time to multimorbidity onset was 1.27 (95% CI: 1.01-1.54) years later for those with high compared to low CRF. Moreover, participants with high CRF experienced a significantly slower annual rate of chronic disease accumulation (β = -0.043 [-0.050 to -0.036]). CONCLUSIONS: High CRF is associated with lower multimorbidity risk, delayed onset of multimorbidity, and significantly slower accumulation of chronic diseases. The findings highlight the importance of CRF for healthy longevity.