Flood Exposure Raises Health Care Use, Costs Among Medicare Beneficiaries

Flood exposure was associated with increased health care use and costs among Medicare beneficiaries aged 65 or older, emphasizing the need for targeted public health strategies and improved disaster preparedness.¹

The authors of the JAMA Network Open study explained that extreme precipitation events have become more frequent and intense over the past century and are expected to increase further due to climate change. They noted that flooding impacts health in various ways, including drowning, electrical injuries, and hypothermia. Additionally, flooding-related infrastructure damage can disrupt health services, displace individuals, and create broader societal challenges.

Older adults may be particularly vulnerable to flooding-related health effects due to preexisting health conditions and mobility limitations, which can hinder their ability to respond to flood warnings or evacuations. This vulnerability is not unique to flooding, as most of the residents confirmed to have died during the California wildfires in January were either aged 65 or older or had a physical disability, underscoring the challenges of evacuation for these populations.²

Floods rank among the costliest disasters in the US, with many causing more than $1 billion in damages.¹ Despite this, the researchers highlighted a lack of understanding regarding the effects of flooding on health care utilization and associated costs, which limits health impact assessments, risk communication, climate change-related damage estimation, and future projections of climate change health impacts.

Flood exposure was more strongly associated with increased health care use and cost during the summer months and among Medicare beneficiaries aged 85 or older. | Image Credit: Rico Löb - stock.adobe.com

To address these gaps, they analyzed the relationship between large-scale flood events and health care use among Medicare beneficiaries aged 65 or older residing in zip code tabulation areas (ZCTAs) affected by such events between 2008 and 2017. More specifically, they examined the incidence of emergency department (ED) visits and hospital admissions during flooding events and assessed the associated health care costs.

The primary exposure variable was the presence of a flood, as recorded in the Multisourced Flood Inventories, a spatially distributed flood database. Also, the primary outcomes measured included incident rate ratios (IRRs) with corresponding 95% CIs.

To quantify the impact, the researchers calculated attributable risk percentages and estimated the number of related excess visits. Additionally, they conducted stratified analyses to assess potential effect modification. As for health care costs, the researchers standardized all estimates to 2017 US dollars to ensure comparability.

The study population contained 11,801,527 Medicare beneficiaries aged 65 or older, with a mean (SD) age of 74.4 (7.6) years. Most beneficiaries were female (56.3%) and White (88.3%). From 2008 through 2017, the researchers determined that 16,536 of 33,140 ZCTAs flooded. The median number of floods experienced in each ZCTA was 1 (IQR, 1-2), and the median flood duration was 10 (IQR, 4-30) days.

The mean (SD) ZCTA flood exposure per beneficiary was 1.3 (0.6). Also, the median area flooded was 34,769 (IQR, 17,319-65,584) square miles, and the median number of Medicare beneficiaries per flooded ZCTA was 4142 (IQR, 2006-7536).

The rate of all-cause ED visits and hospitalizations increased by 4.8% (IRR, 1.05; 95% CI, 1.04-1.05) and 7.4% (IRR, 1.07; 95% CI, 1.07-1.08), respectively, after flood exposure. The researchers observed the largest IRR increases for ED visits among beneficiaries with metabolic and kidney conditions (IRR, 1.08; 95% CI, 1.06-1.11) and injuries (IRR, 1.05; 95% CI, 1.04-1.06). Similarly, they observed the greatest IRR increases for all-cause hospitalizations among beneficiaries with infectious disease (IRR, 1.12; 95% CI, 1.10-1.13) and metabolic and kidney conditions (IRR, 1.10; 95% CI, 1.07-1.12).

Additionally, stratified analyses determined that the IRRs increased with age, from 4.9% greater hospitalizations among adults aged 65 to 74 (IRR, 1.05; 95% CI, 1.04-1.06) to 7.3% higher among those aged 75 to 84 (IRR, 1.07; 95% CI, 1.06-1.08) and 12.4% greater among those aged 85 or older (IRR, 1.12; 95% CI, 1.11-1.1). They also found increased IRRs for ED visits (IRR, 1.07; 95% CI, 1.06-1.10) and hospitalizations (IRR, 1.11; 95% CI, 1.10-1.13) in the summer months.

Lastly, the mean ZCTA-level cost was $3230 (95% CI, $3198-$32,610) per ED visit and $11,310 (95% CI, $11,252-$11,367) for all-cause hospitalizations. Consequently, the national costs to the Medicare system for ED visits and hospitalizations were estimated to be $69,275,429 (95% CI, $63,010,840-$76,315,210) and $191,409,579 (95% CI, $172,782,870-$206,181,300), respectively.

The researchers acknowledged their study’s limitations, including the health care cost estimations using claims data from the Medicare dataset; this approach may not capture the total health care costs resulting from flood exposure. Despite their limitations, they expressed confidence in their findings and suggested areas for further research.

“Although our findings provided valuable insights to the understanding of flood-related health impacts, they also highlighted the need for ongoing research in this area, especially in the context of an aging population and a changing climate,” the authors concluded. “Future studies should aim to incorporate more detailed environmental and individual-level data to further refine our understanding of the complex interplay between flood events and population health.”

References

1. Wettstein ZS, Parrish C, Sabbatini AK, Rogers MH, Seto E, Hess JJ. Emergency care, hospitalization rates, and floods. JAMA Netw Open. 2025;8(3):e250371. doi:10.1001/jamanetworkopen.2025.0371
2. Bonavitacola J. Wildfire evacuations spell difficulties for disabled, elderly residents. AJMC. January 17, 2025. Accessed March 12, 2025. https://www.ajmc.com/view/wildfire-evacuations-spell-difficulties-for-disabled-elderly-residents