Association of flooding exposure with cause-specific mortality in North Carolina, United States

Abstract

Flooding could have a significant impact on 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 (NC), United States (US). 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 to the non-flooding days, the relative risk of deaths associated with flooding exposure was 1.039 (95%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 to the rest of the population (those aged 0-64 years old). More total deaths were attributable to Non-Flash Flood compared to Flash Flood, and more total deaths were attributable to Multiple-day Flood compared to One-day Flood. Compared to One-day Flood, Multiple-day Flood was associated with higher relative risks in all six causes of death (total, non-accidental, 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.