Distinct acute and delayed effects of temperature and atmospheric pressure on allergic rhinitis: a distributed lag non-linear time-series study in subtropical China.

Background: Meteorological conditions are increasingly recognized as important determinants of allergic diseases; however, their temporal dynamics and delayed effects on allergic rhinitis (AR) remain inadequately characterized, particularly in subtropical settings. This study aimed to examine the non-linear and lagged relationships between major meteorological variables and AR-related outpatient visits in Wuxi, a representative subtropical city in eastern China. Methods: A time-series analysis was conducted using data from 76,760 AR outpatient visits recorded in Wuxi, China, between November 2020 and December 2024. Daily meteorological variables, including mean temperature, atmospheric pressure, relative humidity, wind speed, and air pollution indicators were obtained from local monitoring stations. Distributed lag non-linear models (DLNM), coupled with quasi-Poisson regression, were employed to estimate exposure-response relationships and lagged effects, with adjustment for long-term trends, seasonality, and day-of-week effects. Results: AR outpatient visits showed clear seasonal variation, with a major autumn peak and a secondary spring peak, and were predominantly concentrated among children and younger adults. Daily mean temperature was positively and non-linearly associated with AR outpatient visits, with risk increasing progressively above approximately 15 °C. Compared with 15 °C, the cumulative relative risk reached 1.19 at 25 °C and 1.41 at 30 °C, and the association was mainly acute, peaking within lag 0-3 days. In the primary single-exposure DLNM, lower atmospheric pressure showed an inverse exposure-response pattern and a delayed lag structure, with the strongest association observed around lag 8-10 days. However, pressure-related estimates were less stable in co-meteorological-adjusted and age-stratified analyses, suggesting that low atmospheric pressure may reflect broader synoptic weather conditions rather than an isolated independent exposure. Relative humidity and wind speed showed no robust independent associations. Conclusion: In this humid subtropical population, higher temperature was consistently associated with rapid increases in AR outpatient visits. Lower atmospheric pressure showed a delayed association in the primary model, but this pattern was less robust after accounting for correlated meteorological variables and across age strata. These findings provide epidemiological evidence for climate-sensitive AR prevention and support the incorporation of meteorological indicators into seasonal surveillance, early warning systems, and healthcare resource planning.