Background Both cold and hot temperature have been associated with the onset of asthma, but it remains largely unknown about the risk of asthma hospitalisation associated with short-term temperature fluctuation or temperature variability (TV).
Objective To explore the association between short-term exposure to TV and asthma hospitalisation in Brazil.
Methods Data for asthma hospitalisation and weather conditions were collected from 1816 Brazilian cities between 2000 and 2015. TV was calculated as the SD of all daily minimum and maximum temperatures within 0–7 days prior to current day. A time-stratified case-crossover design was performed to quantify the association between TV and hospitalisation for asthma.
Results A total of 2 818 911 hospitalisations for asthma were identified during the study period. Each 1°C increase in 0–7 days’ TV exposure was related to a 1.0% (95% CI 0.7% to 1.4%) increase in asthma hospitalisations. The elderly were more vulnerable to TV than other age groups, while region and season appeared to significantly modify the associations. There were 159 305 (95% CI 55 293 to 2 58 054) hospitalisations, US$48.41 million (95% CI US$16.92 to US$78.30 million) inpatient costs at 2015 price and 450.44 thousand inpatient days (95% CI 156.08 to 729.91 thousand days) associated with TV during the study period. The fraction of asthma hospitalisations attributable to TV increased from 5.32% in 2000 to 5.88% in 2015.
Conclusion TV was significantly associated with asthma hospitalisation and the corresponding substantial health costs in Brazil. Our findings suggest that preventive measures of asthma should take TV into account.
- asthma epidemiology
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Contributors YW performed the main analysis and wrote the original draft. RX, MdSZSC and PHS prepared the data and made substantial contributions to the design of the study. BW assisted the analysis and interpretation of data. SL and YG conceived the study, revised the manuscript and was responsible for funding of the study.
Funding YW, RX, BW were supported by China Scholarship Council (grant number 202006010044, 202006010043, 201806010405) (https://www.csc.edu.cn/chuguo/s/1844, https://www.csc.edu.cn/chuguo/s/1267). SL was supported by the Early Career Fellowship of the Australian National Health and Medical Research Council [grant number APP1109193) (https://www.nhmrc.gov.au/). YG was supported by the Career Development Fellowship of the Australian National Health and Medical Research Council (grant number APP1163693) (https://www.nhmrc.gov.au/).
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval Ethical approval was not required for secondary analysis of aggregate anonymised data from the Brazilian Hospital Information System.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement No data are available.