Abstract
Flooding could adversely impact human health, but its association with different causes of mortality remains unclear. Here we employed a two-stage time series design, utilizing data from 446,807 deaths that occurred during 2015 to 2019, across 98 counties in North Carolina, United States. We first estimated the associations between flooding exposure and cause-specific mortality at the county level and then aggregated those county-level estimates to determine the overall associations at the state level. Compared with the non-flooding days, the relative risk of deaths associated with flooding exposure was 1.039 (95% confidence interval (CI), 0.998–1.083) (one-day lag), 1.046 (95% CI, 1.003–1.092) (one-day lag) and 1.322 (95% CI, 1.166–1.501) (two-day lag) for total, non-accidental and accidental mortality, respectively. Flooding exposure was also associated with mortality risks for cardiovascular disease, respiratory disease and mental disorders. Older adults aged 65 years old and above experienced a significantly higher risk increase in accidental mortality compared with the rest of the population (those aged 0–64 years old). More total deaths were attributable to non-flash flood compared with flash flood, and more total deaths were attributable to multiple-day flood compared with one-day flood. Compared with one-day flood, multiple-day flood was associated with higher relative risks in total death and all the non-accidental causfes of death (non-accidental, cardiovascular, respiratory and mental disorders). If this association is causal, the estimated flood-attributable mortality would be 201 deaths per year, where multiple-day flood contributed 69% and one-day flood contributed 31% of attributable deaths. Our study may contribute to a better understanding of flooding-related health impacts.
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Data availability
Flooding data can be accessed at https://www.ncdc.noaa.gov/stormevents/; daily ambient temperature data can be obtained at https://prism.oregonstate.edu; daily mean precipitation data were obtained from https://www.cpc.ncep.noaa.gov/. Mortality data cannot be shared due to the data confidential limitation but can be obtained from the North Carolina State Center for Health Statistics.
Code availability
All analyses reported in this study used the statistical software R (version 4.2.2). The code used for the main analysis is available at https://github.com/CHENlab-Yale/Flood_mortality_NC/.
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Acknowledgements
J.B. was supported by the Li Foundation Climate Change Fellowship Program at the Yale Center on Climate Change and Health.
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J.B. designed the study, implemented analyses and drafted the manuscript; K.C. designed the study, conceived of and supervised the conduct of this study and edited the manuscript. Y.M. and C.L. applied and cleaned the precipitation and temperature data; C.S. contributed to the writing and manuscript revision. All authors approved the final version of this paper.
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Ban, J., Sutton, C., Ma, Y. et al. Association of flooding exposure with cause-specific mortality in North Carolina, United States. Nat Water 1, 1027–1034 (2023). https://doi.org/10.1038/s44221-023-00167-5
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DOI: https://doi.org/10.1038/s44221-023-00167-5
