A case-crossover study of relationship between heat wave and hospital admission and readmission for type 2 diabetes in Beijing, China

Objective To investigate the effect of heatwaves on daily hospital admissions and readmissions for type 2 diabetes among local residents in Beijing, China.

Methods A time-stratified case-crossover design was used to collected data on hospital admissions and readmissions for type 2 diabetes, meteorological factors, and air pollutants in Beijing during each summer(June to August) of 2013—2017. A conditional logistic regression model was used to quantitatively analyze the influence of heat waves on daily admissions and readmissions for type 2 diabetes and its lag effects during the study period among Beijing residents, and further compare the effects of heat waves (mild and extreme heat wave events) on different sexes, ages, and places of residence. With at least one week before or after admission and readmission were selected as a time interval to match the cases with the corresponding control, the odds ratio (OR) and its confidence interval (CI) were calculated to reflect the degree of impact of heat waves on hospital admissions and readmissions for type 2 diabetes.

Results During summer of 2013 to 2017, there were 34 378 admissions and 6 501 readmissions for type 2 diabetes in 16 municipal districts of Beijing. On the day of a mild heatwave lasting more than 2 days, the risks of admission and readmission for type 2 diabetes relative to non-heatwave days significantly increased, with OR being 1.03 (95%CI: 0.99, 1.07) and 1.10 (95%CI: 1.01, 1.20), respectively. The stratified analyses of mild heatwave exposure in different subgroups revealed that female residents had a higher risk of hospital admission or readmission for type 2 diabetes than male residents, and those aged 40 to below 59 years showed a higher risk of admission or readmission for type 2 diabetes than other age groups.

Conclusion Heat waves had a significant impact on admission and readmission of type 2 diabetes, with the greatest risk occurring on the first day (lag 0) of heat wave exposure. Mild heat waves imposed a higher risk of type 2 diabetes admission and readmission than extreme heat waves. During heat waves, the risk of readmission for type 2 diabetes was higher than the risk of admission for type 2 diabetes.