Association between cold spells and frailty among middle-aged and older adults in China: Evidence from a national longitudinal survey

Background Frailty is a multifaceted clinical syndrome associated with adverse health outcomes. Cold spells, as acute environmental stressors, may expedite the development of frailty. The study aimed to explore the association of cold spells and risk of frailty among older people Methods Using data from the China Health and Retirement Longitudinal Study (CHARLS), we conducted a prospective cohort study of 13,578 adults aged ≥ 45 years from 2011 to 2018. Cold spell exposure was assessed using city-level meteorological data and defined by site-specific temperature percentiles (≤ 7.5%, 5%, and 2.5%) and duration (≥ 2, 3, and 4 days). Cox proportional hazard models incorporating time-dependent covariates were utilized to evaluate the impacts of cold spells events on the risk of frailty. Additionally, subgroup analyses were carried out to assess potential modifying effects across various populations. Results Across all intensity and duration definitions, each one-unit increase in the natural log-transformed number of cold spell days was associated with a 12.3% (95% CI: 1.089–1.158,) to 14.4% (95% CI: 1.104–1.185) higher risk of frailty after full adjustment. Subgroup analyses revealed stronger associations among older individuals, female, non-drinkers, and those residing in southern regions. Conclusion This study provides robust evidence that cold spells contribute to the development of frailty among middle-aged and older adults in China. The effects were more pronounced in specific subpopulations, indicating the need for targeted public health interventions and regionally adapted cold weather preparedness strategies.