Effects of temperature on daily hospital visits for urticaria in Nanchang, China: a distributed lag nonlinear time series analysis

This study evaluated temperature's lagged effects on urticaria outpatient visits in Nanchang, China (2017-2022), and identified sensitive populations through age/gender stratification. Using a distributed lag nonlinear model (DLNM), we analyzed 71,779 urticaria visits, adjusting for humidity, weekday, holidays, and seasonal/long-term trends. Temperature effects (cold: 5th/25th percentiles; hot: 75th/95th percentiles) were compared to the 50th percentile. Temperature exhibited non-linear and delayed impacts. Daily averages >19.9°C initially increased then decreased urticaria risk, peaking at 29°C with a 15-day lag (RR=1.74, 95% CI:1.63-1.86). No adverse effects occurred below 19.9°C. Individuals aged ≥60 were most vulnerable: at 29°C with a 16-day lag, RR surged to 2.31 (95% CI:1.99-2.70). Hot increases urticaria outpatient visits, while cold reduces risk. These findings highlight temperature-specific prevention strategies, particularly for older adults.