Objective To investigate the impact of extremely high temperature on outpatient visits in 18 districts/counties of China, and to identify diseases sensitive to extremely high temperature and vulnerable populations.
Methods Related data in 2014-2018 were collected, including daily outpatient data, meteorological data, and air pollution data. After control for the confounding factors including relative humidity, long-term trend, and holidays/festivals, the distributed lag non-linear model was used in the first stage to estimate the exposure-respond relationship between extremely high temperature and daily outpatient visits in each region, and then in the second stage, a multivariate meta-regression analysis was used for the pooled exposure-respond coefficients of the data from all hospitals to analyze the influence of extremely high temperature on the daily outpatient visits for different etiologies, sexes, and ages.
Results A total of 13 045 586 outpatient cases were collected. Extremely high temperature had a statistically significant effect on the daily outpatient visits of respiratory diseases, digestive diseases, endocrine diseases, skin diseases, and injury, with a 2-week accumulative relative risk (CRR) of 1.235 (95% CI: 1.014-1.505), 1.109 (95% CI: 1.012-1.215), 1.141 (95% CI: 1.006-1.294), 1.199 (95% CI: 1.064-1.351), and 1.157 (95% CI: 1.013-1.321), respectively. The CRR of the effect of extremely high temperature on male and female were 1.158 (95% CI: 1.033-1.302) and 1.110 (95% CI: 1.024-1.197), respectively. Extremely high temperature had a statistically significant effect on the age groups of 7-17, 18-44, and 60-74 years, with the CRR of 1.352 (95% CI: 1.087-1.683), 1.116 (95% CI: 1.041-1.195) and 1.119 (95% CI: 1.016-1.232), respectively.
Conclusion Extremely high temperature can increase the risk of various diseases. Male is more sensitive to extremely high temperature than female, and, the age groups of 7-17, 18-44, and 60-74 years are vulnerable populations.
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