The Combined Effects of Long-Term Mixture Exposure to Temperature and Relative Humidity on Asthma in China

Background: Few previous stud ies ha ve examined the joint effect of long term exposure to temperature and relative humidity ( RH on ast hma This study endeavors t o explore the combined association between long term co exposure to temperature and R H and asthma in China.

Methods: The individual data of asthma were collected from the wave 1 to wave 3 (2007 2019) of the Study on global AGEing and adult health in China. M eteorological factors data were obtained from the European Center for Medium range Weather Forecasts Reanalysis 5 (ERA5) and extracted from the corresponding interpolated grid according to individual residential latitude, longi tude and survey time. Individual and joint association of long term exposure to annual mean temperature and RH with asthma were estimated using Cox regression model and Quantile Based g Computation model Q gcomp)gcomp), respectively Then , the joint effects of different temperature RH compound events w ere further estimated

Results: We observed negative association between both temperature and RH with asthma. In individual effect analysis, for 1 °C or 1% decrease in 3 year average temperature and RH , asthma increased 4 44 (95% 1 76 7 0 5) and 6 45 (95% 2 79 9 98 respectively. The joint effect of long term exposure to temperature and RH on asthma was also negative . F or each percentile decreasing of both temperature and RH asthma decreased 1.50% (95%CI: 0.85% 2.15%) in total population . People 60 years old and female were more susceptible to mixture exposure to low temperature and low RH. W e also observed a higher risk of asthma in dry cold event ( 2.44 , 95%CI: 1 67 3 55 than wet cold, wet hot and dry hot events

Conclusion: Long term exposure to t emperature and RH may jointly associate with asthma , and low RH and cold may have higher risk on asthma onset .