Impacts of exposure to humidex on the risk of childhood asthma hospitalizations in Hefei, China: Effect modification by gender and age

Abstract Background With global climate change, there is growing concern about the effects of temperature changes on childhood asthma. However, current research only focuses on the effects of temperature, while ignoring the adverse effects of humidity on children. Objectives Our study aimed to quantify the impact of humidex on childhood asthma hospitalizations, which combined temperature and humidity, and further to assess how the effect is modified by individual-factors, such as age and gender. Methods Poisson generalized linear models combined with distributed lag nonlinear models were used to estimate the association between daily childhood asthma hospitalizations and humidex from 2013 to 2016. Air pollutions (CO, O 3, and NO 2 ) and wind velocity were modelled simultaneously using DLNM, as well as day of week, seasonality and long-term trend. Results Low humidex was associated with an increased risk of admissions for asthma in children. The adverse effect appeared on the 4th day, with the RR of 1.045 (95% CI : 1.007–1.084) and lasted until the 7th day ( RR : 1.045, 95% CI : 1.006–1.085). Compared with the male, there was an immediate effect on female exposed to low humidex. And the female seems to be more sensitive to low humidex. Besides, the significant effects of humidex on children asthma were detected in the children with preschool and school-age, whereas not for the subgroup of infants. And the school-age children are most sensitive to low humidex. Conclusions Low humidex was associated with the increased risk of admissions for childhood asthma in Hefei. Children suffering from asthma should avoid exposure to the low humidex environment, especially in female and school-age children. In addition, the index of humidex was more significant for disease prevention and public health than the average temperature. These findings may provide epidemiology evidence for formulating precaution guidelines to reduce the risk of childhood asthma hospitalizations.