Frailty transitions and the risk of multisystem burden of chronic disease: a prospective cohort study in China

Frailty, defined by a decline in physiological reserve, is a key determinant of adverse health outcomes in older populations. While baseline frailty has been shown to predict the development of chronic diseases, the impact of changes in frailty status over time, particularly in rapidly ageing populations like China, remains poorly understood. This study aimed to assess how baseline frailty and its longitudinal transitions influence the incidence of chronic diseases across multiple organ systems. We analysed data from 17,708 adults (aged ≥ 40) in the China Health and Retirement Longitudinal Study (CHARLS) collected between 2011 and 2018. Frailty was assessed using the Rockwood Frailty Index at baseline and at two-year follow-up, categorised as stable, improved, or worsened. We applied Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the onset of 13 major chronic diseases spanning cardiovascular, metabolic, respiratory, neurological, psychiatric, digestive, renal, and musculoskeletal systems. The study included 9,807 to 16,882 participants across 13 disease-specific subgroups, with a median follow-up period of 6.2–6.8 years for baseline frailty status and 4.4–5.0 years for frailty transitions. Frail individuals were typically older, more likely to be female, unmarried, with lower education, higher BMI, and reported fewer hours of sleep. Baseline frailty was associated with significantly higher risks for all 13 chronic diseases, with the strongest association observed for psychiatric problems (HR 5.17, 95% CI 3.24–8.24). Worsening frailty over time was linked to elevated risks, particularly for asthma (HR 3.91, 95% CI 1.28–11.91), while improvements in frailty showed reduced risks, notably for kidney diseases (HR 0.37, 95% CI 0.22–0.63). The association was particularly strong in adults aged 40–65 years, indicating greater potential for risk modification in midlife. Frailty is a dynamic and modifiable predictor of multisystem chronic disease risk. Changes in frailty status offer valuable insights into future disease development, especially among middle-aged adults. Routine frailty monitoring in clinical settings may offer a strategic opportunity to delay or prevent the onset of chronic diseases through timely interventions. These findings emphasize the need for incorporating frailty-targeted strategies into public health and clinical care policies to enhance ageing-related disease prevention.