Over recent decades, there has been a large variation in cyclone-related excess deaths by hurricane, state, county, year, and social vulnerability across the United States, with 83 percent of hurricane-related deaths occurring more recently and 94 percent in more socially vulnerable counties.
A new study published in the journal Science Advances has found that tropical cyclones caused thousands of excess deaths in the United States over a period of 32 years.
Named tropical storms and hurricanes, which have become more intense, have caused about 20,000 more deaths from 1988 to 2019, according to the study, which exemplifies how variable the impacts of even the same tropical cyclone have been, driven differences in by demographic, economic, and social factors.
Total excess deaths were particularly high in counties with the largest proportion of minorities. Until now, there had been a critical knowledge gap about estimating post-cyclone excess deaths with a consistent methodology from a large-scale study covering the entire United States across multiple decades.
About 20,000 excess deaths – the number of observed rather than expected deaths – occurred in the immediate aftermath of 179 named storms and hurricanes which struck the US mainland between 1988 and 2019.
“Cyclones don’t hit the whole country. They tend to hit places which have more Black, Indigenous and Latin people who’ve been historically underserved and overburdened through racism, and it’s these socially vulnerable communities who are bearing the brunt of post-cyclone excess deaths,” said Robbie Parks, assistant professor of environmental health sciences at Columbia University’s public health school and lead author.
The researchers found that the single largest number of excess deaths was in Orleans Parish, LA, after Hurricane Katrina in 2005, with 719 excess deaths. followed by Harris County, TX, after Hurricane Rita in 2005 (309 excess deaths), Broward County, FL, after Hurricane Matthew in 2016 (185 excess deaths), and Nassau County, NY, after Hurricane Sandy in 2012 (178 excess deaths). Full results of the top-20 most impacted counties and associated year and hurricane can be found in the table below.
40.7 million U.S. deaths and a comprehensive record of 179 tropical cyclones over 32 years
The study, which was led by researchers at the University of California, Berkeley, used death registration data to estimate the number of deaths that occurred in the immediate aftermath of tropical cyclones, above and beyond the number of deaths that would have occurred if the cyclones had not happened.
The study found that the deadliest tropical cyclone in the United States during the study period was Hurricane Katrina, which struck the Gulf Coast in 2005. Katrina was responsible for an estimated 1,491 excess deaths. Other major tropical cyclones that caused significant excess deaths included Hurricane Sandy (2012), Hurricane Harvey (2017), and Hurricane Maria (2017).
The study also found that the risk of excess mortality from tropical cyclones was highest in the immediate aftermath of the storm, and that the risk declined over time. However, even several months after a tropical cyclone, the risk of death remained elevated.
The study’s findings highlight the significant public health burden of tropical cyclones. The researchers call for better preparedness and mitigation measures to reduce the risk of excess mortality from these storms.
Key findings of the study include:
- Tropical cyclones caused over 14,000 excess deaths in the United States over a period of 32 years.
- The deadliest tropical cyclone in the United States during the study period was Hurricane Katrina.
- The risk of excess mortality from tropical cyclones was highest in the immediate aftermath of the storm, and that the risk declined over time.
- Even several months after a tropical cyclone, the risk of death remained elevated.
The study’s findings highlight the significant public health burden of tropical cyclones. The researchers call for better preparedness and mitigation measures to reduce the risk of excess mortality from these storms.
These measures could include:
- Building codes that make homes and businesses more resilient to hurricanes and other tropical cyclones.
- Evacuation plans that ensure that people are able to safely leave areas that are at risk of being hit by a tropical cyclone.
- Public education campaigns that teach people about the risks of tropical cyclones and how to stay safe.
By taking these steps, we can help to reduce the number of deaths caused by tropical cyclones.
The most estimated excess deaths in a single year were during 2005, with 2,163 estimated post-tropical cyclone excess deaths, with 1,491 from Hurricane Katrina in 2005. Where probabilities of excess deaths were high, 83 percent of post-hurricane-force and 70 percent of post-gale-to-violent-storm-force excess deaths occurred more recently (2004–2019); and 94 percent were in more socially vulnerable counties.
“In our study, excess death counts after tropical cyclones were higher more recently and for the most socially vulnerable,” said Robbie M. Parks, PhD, assistant professor of Environmental Health Sciences at Columbia Public Health, and first author. “This was likely in part due to lack of access to adequate short-term transportation, as well as inequitable access to financial resources, education, employment opportunities and timely warnings on tropical cyclone proximity, all of which are results of long-term institutional neglect.”
Knowledge of short-term excess deaths—i.e., the difference between the observed number of deaths in the immediate aftermath post-tropical cyclone and the number of deaths had a cyclone not occurred—is essential for understanding the public health burden of climate-related disasters and a key recommended measure for post-disaster mortality assessment, note the authors.
Following a tropical cyclone, deaths can result from several major causes, including deaths from injuries, infectious and parasitic diseases, cardiovascular diseases, neuropsychiatric conditions, and respiratory diseases. In earlier research published In JAMA and Nature Communications, Parks and colleagues detailed the kinds of causes and risks for death which increased after tropical cyclones.
Using death registration data across four decades and an ensemble of 16 Bayesian statistical models, the researchers estimated the number of excess deaths after tropical cyclones in all impacted areas in the U.S. including estimates by county, year, tropical cyclone name, and strength of tropical cyclone.
Estimated excess deaths in the study were also compared to data from official sources and EM-DAT, the international disaster database.
“Trends of heightened activity and increased intensity of tropical cyclones in recent years indicate that tropical cyclone exposure is and will remain a public health concern,” noted Marianthi-Anna Kioumourtzoglou, ScD, associate professor of Environmental Health Sciences at Columbia Mailman, and senior author. “Future research may be able to study associations by smaller areal units—ZIP Codes, for example—as appropriate exposure and outcome data become available. It is also essential to prepare for tropical cyclones by accounting for the social determinants of risk and vulnerability of exposed communities, since the most socially vulnerable bear the greatest burden of excess mortality.”
“Our work highlights how deaths are impacted by tropical cyclones, an understudied exposure in relation to public health, and one which will remain an important threat as the climate changes,” observed Parks. “As a public health priority, future research should focus on understanding the biological and structural drivers of cyclone-related mortality, how to minimize the number of excess deaths related to tropical cyclones, and the impacts on the scale from years to decades.”
Co-authors are Vasilis Kontis, Ralf Toumi, and Majid Ezzati, Imperial College London; G. Brooke Anderson, Colorado State University; Jane W. Baldwin, University of California, Irvine, and Columbia Lamont-Doherty Earth Observatory; Goodarz Danaei and Francesca Dominici, T. H. Chan School of Public Health, Harvard.