Citation

Sheridan P, McElroy S, Casey J, Benmarhnia T. Epidemiology 2022; ePub(ePub): ePub.

Copyright

(Copyright © 2022, Lippincott Williams and Wilkins)

DOI

10.1097/EDE.0000000000001539

PMID

36166207

Abstract

BACKGROUND: Traditional epidemiologic approaches such as time-series or case-crossover designs are often used to estimate the effects of extreme weather events but can be limited by unmeasured confounding. Quasi-experimental methods are a family of methods that leverage natural experiments to adjust for unmeasured confounding indirectly. The recently developed generalized synthetic control method that exploits the timing of an exposure is well suited to estimate the impact of acute environmental events on health outcomes. To demonstrate how this method can be used to study extreme weather events, we examined the impact of the October 20th - 26th 2007 Southern California wildfire storm on respiratory hospitalizations.

METHODS: We used generalized synthetic control to compare the average number of ZIP code-level respiratory hospitalizations during the wildfire storm between ZIP codes that were classified as exposed versus unexposed to wildfire smoke. We considered wildfire exposure eligibility for each ZIP code using fire perimeters and satellite-based smoke plume data. We retrieved respiratory hospitalization discharge data from the Office of Statewide Health Planning and Development. R code to implement the generalized synthetic control method is included for reproducibility.

RESULTS: The analysis included 172 exposed and 578 unexposed ZIP codes. We estimated that the average effect of the wildfire storm among the exposed ZIP codes was an 18% (95% CI: 10%-29%) increase in respiratory hospitalizations.

CONCLUSIONS: We illustrate the use of generalized synthetic control to leverage natural experiments to quantify the health impacts of extreme weather events when traditional approaches are unavailable or limited by assumptions.

Language: en