Staying put after a natural disaster is known to bring health risks. Now, scientists have calculated how much higher mortality risk from all causes is for people, aged over 65 and covered by health insurance, who continued to live for up to five years in areas that flooded after Hurricane Sandy’s landfall in 2012. On average, risk of death from all causes for these tri-state area residents increased by 9%, compared to those who lived in not flooded zip codes. Stark regional differences were found between some regions, which makes region-specific disaster planning crucial, the team said.

Hurricanes and related natural catastrophes like flooding are becoming more severe and more frequent around the world. Older people are especially at risk, but relatively little is known about long-term health effects. In 2012, the north-east US was hit by Hurricane Sandy, which resulted in unusable transportation systems, destruction of homes, power loss, and more than 100 casualties.

But what about the people who continue living in hurricane-mangled areas? Now, researchers in the US have investigated if staying put after the landfall of Sandy increased mortality risk from all causes among health-insured people aged 65 or above.

“We show that areas impacted by hurricane-related flooding after Hurricane Sandy had higher rates of mortality from any reason,” said Dr Arnab Ghosh, senior author of the Frontiers in Public Health study who is an assistant professor of medicine at Cornell University. “Hurricane flood exposure was linked to a 9% increased risk of death for those residing in hurricane flooded areas up to five years after landfall.”

Risky zip codes

The team split parts of New York State, New Jersey, Connecticut, and New York City – the areas that were most affected – into 959 zip-code tabulation areas (ZCTAs). 454 of these ZCTAs had been impacted by flooding, the others were within a 10-mile radius of flooded ZCTAs. The researchers used data from almost 300,000 people aged 65 or older who were enrolled in the US federal health insurance program (Medicare parts A and B) and had continued to reside in the same zip code area from 2013 to 2017. They controlled for various demographic and socioeconomic factors for all ZCTAs, including age, gender, race, and living circumstances.

The researchers focused on older adults due to their increased vulnerability in the aftermath of extreme weather, which may include higher rates of medical comorbidities, functional limitations, and cognitive impairment compared to younger people. In addition, this demographic group is fast-growing, and likely will be requiring more assistance during and after future disasters.

The results showed that Medicare beneficiaries who stayed in flooding-impacted ZCTAs in the tri-state area had a significantly higher risk – 9% on average – of death from all causes up to five years after the hurricane hit than people living in flooding-unaffected zip codes. “Our findings underscore the importance of considering long-term health impacts of hurricane-related flooding on older adults, and the need to reconsider how disasters impact people’s lives in the longer term,” said Ghosh.

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Localized disaster response

Previous studies had shown that risk of death from any cause can rise after natural disasters, but the geographic distribution of increased risk surprised the researchers. Risk of death increased the most for people living in flooded areas in Connecticut and New York City, by 19% and 8%, respectively, compared to people living in non-flooded areas. “We were surprised by the finding that two socioeconomically different regions both exhibited significant effects on mortality risk. This emphasizes the importance of region-specific considerations,” explained Ghosh.

While New York City ZCTAs have been associated with socioeconomic and demographic characteristics that may result in greater exposure to natural disasters, the same characteristics cannot be found in Connecticut, where more White people whose average household income is higher live in less overcrowded homes. Yet, out of the studied regions, Connecticut had the highest mortality risk increase between flooded ZCTAs and non-flooded ZCTAs. The reasons for this regional variation needs to be investigated in further studies, the team said. “It’s possible that regional nuances in Connecticut influence long-term mortality effects post-flood,” said Ghosh. “This could include region-specific policies, infrastructure disruption, and disaster relief.” In New Jersey and New York State risk of death from any cause didn’t increase significantly between ZCTAs.

These findings do not extend to individual mortality risk, the researchers said. Disaster preparedness often focuses on population risk, so understanding long-term risks on this level is crucial. “As disasters hit the same regions again and again, understanding how and why vulnerable populations are more likely to be adversely impacted will be clearly important, and our study helps explain why,” Ghosh concluded.

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