Associations of extreme temperature and relative humidity with hematological disease mortality in Chuzhou, China

Abstract

This study aims to quantify the associations between extreme temperatures, relative humidity, and mortality risk in patients with hematological diseases within a subtropical urban environment, and to identify vulnerable demographic subgroups. We conducted a time-series analysis using data from Chuzhou, China, spanning 2019 to 2024. Daily mortality counts for hematological diseases (ICD-10 codes C82-C95), meteorological variables (daily mean temperature and relative humidity), and air pollution data were analyzed. A Poisson generalized linear model combined with a distributed lag nonlinear model (DLNM) was applied to assess nonlinear and delayed effects, with adjustments for long-term trends, day of the week, and air pollutants. Stratified analyses were performed by age and gender. A total of 1,651 hematological disease deaths were included. A U-shaped relationship was observed between daily mean temperature and mortality, with minimum risk at approximately 22 °C. Extreme heat exhibited a delayed but prolonged effect, with risk emerging after 7 days and persisting. In contrast, extreme cold triggered a more immediate response, with significant risk appearing at lag 5 days. An optimal relative humidity threshold was identified at 76%. Both high and low humidity increased mortality risk, with low humidity showing an earlier effect (lag 2 days) than high humidity (lag 5 days). Stratified analyses revealed males and younger individuals (< 65 years) were particularly vulnerable to these environmental stressors. Extreme temperatures and abnormal humidity levels are significant environmental risk factors for mortality in hematological disease patients, with distinct temporal patterns and demographic variations. These findings underscore the need to incorporate this vulnerable population into climate‑adaptive public health strategies.