Effects of Temperature on Outpatient Visits for Urticaria among Lanzhou Residents Based on Distributed Lag Non-linear Model

Abstract

Objective To evaluate the influence of temperature on the outpatient visits for urticaria in Lanzhou City and its hysteresis and to find out the sensitive populations by sex and age stratification.Methods We collected the urticaria outpatient data in three grade A class three hospitals as well as the meteorological data and air pollutant data in Lanzhou from January 2011 to December 2017.The distributed lag non-linear model(DLNM)was employed to analyze the influence of daily mean temperature on the outpatient visits for urticaria.Stratification analysis was performed for different age groups(0-14,15-59,≥60 years)and different sex populations.Results Temperature had a non-linear relationship with the outpatient visits for urticaria,and there existed hysteresis.During the research period,the average daily outpatient visits for urticaria at the three hospitals in Lanzhou was 25,ranging from 1 to 76.With the rise in the daily mean temperature within 0-10 ℃,the risk of outpatient visits for urticaria first increased and then decreased.When the daily mean temperature was 2 ℃,hysteresis occurred on the 18th day,and the relative risk(RR)reached the maximum(1.12,95% CI:1.04-1.20)at the lag of 21 days.The risk of urticaria increased with the rise in temperature at high temperature.In addition,the effect of high temperature on the outpatient visits for urticaria in Lanzhou presented hysteresis,and the hysteresis was more obvious at higher temperatures.At the lag of 21 days,when the temperatures were 19.9 ℃ and 25.5 ℃,the RR values were 1.20(95% CI:1.12-1.27)and 1.39(95% CI:1.31-1.48),respectively.The results of stratified analysis showed that the effect of high temperature was more sensitive for those of 0-14 years and 15-59 years as well as the female population,and the RR values at a lag of 21 days were 1.60(95% CI:1.45-1.71),1.34(95% CI:1.25-1.43),and 1.43(95% CI:1.33-1.53)for the population of 0-14 years,the population of 15-59 years,and female population,respectively.Low temperature mainly affected the people aged ≥60 years,with a maximum RR of 1.38(95% CI:1.03-1.85)when the daily mean temperature was -4.8 ℃ at a lag of 12 days.It did not affect other populations.Conclusions The daily mean temperature in Lanzhou share a close relationship with the outpatient visits for urticaria.High temperature will increase the risk of urticaria for people at the age of 0-14 years and 15-59 years,while low temperature will increase the risk of urticaria for people above 60 years.