Large floods drive changes in cause-specific mortality in the United States

Abstract

Flooding greatly endangers public health and is an urgent concern as rapid population growth in flood-prone regions and more extreme weather events will increase the number of people at risk. However, an exhaustive analysis of mortality following floods has not been conducted. Here we used 35.6 million complete death records over 18 years (2001-2018) from the National Center for Health Statistics in the United States, highly resolved flood exposure data and a Bayesian conditional quasi-Poisson model to estimate the association of flooding with monthly county-level death rates for cancers, cardiovascular diseases, infectious and parasitic diseases, injuries, neuropsychiatric conditions and respiratory diseases up to 3 months after the flood. During the month of flooding, very severe heavy rain-related floods were associated with increased infectious disease (3.2%; 95% credible interval (CrI): 0.1%, 6.2%) and cardiovascular disease (2.1%; 95% CrI: 1.3%, 3.0%) death rates and tropical cyclone-related floods were associated with increased injury death rates (15.3%; 95% CrI: 12.4%, 18.1%). During the month of very severe tropical cyclone-related flooding, increases in injury death rate were higher for those ≥65 years old (24.9; 95% CrI: 20.0%, 29.8%) than for those aged <65 years (10.2%; 95% CrI: 6.6%, 13.8%) and for females (21.2%; 95% CrI: 16.3%, 26.1%) than for males (12.6%; 95% CrI: 9.1%,16.1%). Effective public health responses are critical now and with projected increased flood severity driven by climate change.

Fig. 1. Total deaths by cause of death, sex and age group in the United States during 2001–2018.

All deaths in counties that experienced at least one flood event (n = 2,711 counties) during the study period.

Fig. 2. Total count of flood events per county by flood causes during 2001–2018.

a, Heavy rain flood events (n = 61). b, Tropical cyclone flood events (n = 18). c, Snowmelt flood events (n = 9). d, Ice jam or dam break flood events (n = 5).

Fig. 3. Percentage change in all-cause death rates.

Percentage change in all-cause death (n = 35,613,398) rates per flood event by flood cause, flood severity and lag time. Lag time is measured in months after flood event. Dots show the mean point estimates, and error bars represent 95% CrI.

Fig. 4. Percentage change in cause of death-specific death rates.

Percentage change in death (n = 35,613,398) rates per flood event by flood cause, flood severity, cause of death and lag time. Lag time is measured in months after flood event. Dots show the mean point estimates, and error bars represent 95% CrI.

Fig. 5. Percentage change in cause of death-specific death rates associated with very severe floods by sex.

Percentage change in death (n = 35,613,398) rates per very severe flood event by flood cause, cause of death, sex and lag time. Lag time is measured in months after flood. Dots show the mean point estimates, and error bars represent 95% CrI.

Fig. 6. Percentage change in cause of death-specific death rates associated with very severe floods by age category.

Percentage change in death (n = 35,613,398) rates per very severe flood event by flood cause, cause of death and age category. Dots show the mean point estimates, and error bars represent 95% CrI.

Extended Data Fig. 1. Age-standardized death rates during 2001–2018.

Age-standardized death rates per 100,000 by month and year for each cause of death and by sex during 2001–2018.

Extended Data Fig. 2. Count of flood events by month and flood cause during 2001–2018.

Number of flood events by flood cause (heavy rain, tropical cyclone, snowmelt, and ice jam or dam break) and month during 2001–2018.

Extended Data Fig. 3. Percentage change in death rates.

Percentage change in death rates per flood event by cause of death, flood severity, and lag time. Lag time is measured in months after flood. Dots show point estimates and error bars represent 95% credible intervals.

Extended Data Fig. 4. Median flood duration in days.

Median flood duration in days by county and flood cause during 2001–2018. Panel A: heavy rain flood events (n = 61); Panel B: tropical cyclone flood events (n = 18); Panel C: snowmelt flood events (n = 9); Panel D: ice jam or dam break flood events (n = 5).

Extended Data Fig. 5. Median maximum flood duration in days.

Median maximum flood duration in days by county and flood cause during 2001–2018. Panel A: heavy rain flood events (n = 61); Panel B: tropical cyclone flood events (n = 18); Panel C: snowmelt flood events (n = 9); Panel D: ice jam/dam break flood events (n = 5).