When Floods and Blackouts Strike Together, Heart Hospitalizations Surge

When a major storm rolls ashore, the damage rarely stops at flooded streets and downed power lines. A new study from New York State suggests that the most dangerous moments may come when two hazards overlap: rising water and failing electricity. Researchers analyzing more than a decade and a half of hospital records found that while floods and power outages each raise the risk of cardiovascular hospitalization on their own, the risk climbs noticeably higher when the two strike the same communities at the same time. The findings, published in the Journal of Exposure Science & Environmental Epidemiology, offer some of the clearest evidence yet that compound environmental hazards can impose a measurable toll on the human heart, and that this toll falls hardest on older adults, rural residents, and people with limited access to health insurance.

The research team, led by Yineng Chen and Shao Lin of the University at Albany, State University of New York, drew on an unusually rich set of data sources to untangle the relationship between flooding, blackouts, and heart disease. Hospitalization records came from the Statewide Planning and Research Cooperative System, a comprehensive database covering patients across New York State from 2005 through 2021. Flood events were identified using the National Oceanic and Atmospheric Administration’s Storm Events Database, while power outage information was supplied by the New York Department of Public Service. To account for other factors that could confound the association, the researchers incorporated fine particulate matter concentrations modeled with the Community Multiscale Air Quality system, meteorological variables from the New York State Mesonet and the Integrated Surface Database, and a suite of time-varying factors such as seasonality and long-term trends.

Methodologically, the study relied on distributed lag nonlinear models embedded within a quasi-Poisson regression framework, a statistical approach widely used in environmental epidemiology to capture how health risks change over time after an exposure and how those risks may behave nonlinearly with increasing hazard intensity. This design allowed the team to estimate the independent effect of flooding, the independent effect of power outages, and the joint effect of their co-occurrence, all while adjusting for air pollution, weather conditions, and temporal patterns that might otherwise masquerade as hazard effects. The researchers also examined hospital length of stay, treatment costs, comorbid conditions, and threshold levels of exposure, and they compared the periods before and during the COVID-19 pandemic to see whether the pandemic altered the hazard-health relationship.

The headline result is deceptively simple: co-occurrence matters. Flooding and power outages were each independently associated with hospitalizations for total cardiovascular disease and for specific cardiovascular subtypes, but the association was strongest when both hazards occurred together, with the highest relative risk reaching 1.09 (95 percent confidence interval: 1.03 to 1.15). In epidemiological terms, that corresponds to roughly a nine percent increase in cardiovascular hospitalization risk during compound events compared with periods without these hazards. While a nine percent increase may sound modest, cardiovascular disease is the leading cause of death in the United States, and even small proportional increases translate into substantial numbers of excess hospital admissions when large populations are exposed, as they are during major storms that knock out power across entire regions.

Equally important are the thresholds the study identified. Cardiovascular risk rose when flooding persisted for more than three days, and when power outages affected more than 15.3 percent of a community. These cutoffs provide concrete, actionable benchmarks for emergency managers: rather than treating all flood and outage events as equally threatening, preparedness efforts can be concentrated on events that cross these critical windows. The researchers also found that flood and outage events were associated with longer hospital stays and higher levels of comorbidity among admitted patients, suggesting that compound hazards not only push more people into hospitals but may also produce more complicated, resource-intensive admissions.

The burden was not distributed evenly across the population. Stratified analyses revealed stronger joint effects for several cardiovascular subtypes, including hypertension, stroke, and ischemic heart disease. The risks were also amplified among people over 65 years of age, individuals enrolled in Medicaid or lacking insurance coverage, and residents of rural communities. These patterns align with what is known about vulnerability to disasters: older adults are more likely to have preexisting cardiovascular conditions and to depend on electricity-powered medical devices, while rural communities often face longer emergency response times, older infrastructure, and fewer backup resources. Socioeconomically disadvantaged groups, meanwhile, may have less capacity to evacuate, stockpile medications, or weather prolonged outages safely, a disparity documented in prior research on disaster preparedness among older adults.

Season and timing mattered as well. The joint effects of flooding and outages were strongest during winter and spring, seasons when cold temperatures place additional strain on the cardiovascular system. Blood pressure is known to rise in colder conditions, and the physiological stress of a cold, dark, flooded home can compound that burden. Winter storms in the Northeast are also notorious for triggering both flooding and widespread outages simultaneously, meaning the compound-exposure scenario the study examines is not a rare curiosity but a recurring feature of the regional hazard landscape. River flood seasonality in the northeastern United States, concentrated in these colder months, helps explain why the overlap is so common.

The pandemic comparison added a further layer of complexity. The joint occurrence of flooding and power outages showed a larger risk of cardiovascular hospitalization during the COVID-19 period than before it, although the difference was not statistically significant. The authors note that the pandemic disrupted routine healthcare utilization, altered hospital admission patterns, and may have increased the underlying cardiovascular vulnerability of the population, since COVID-19 itself has been linked to cardiovascular complications. The direction of the finding, even without statistical significance, hints that health systems under strain may be less able to absorb the shocks of compound environmental hazards, a concern that resonates as climate change intensifies extreme weather while health systems face recurring pressures.

What makes this study particularly valuable is its shift in perspective. Most environmental health research examines one hazard at a time, estimating the risk of floods here and outages there, as if the world kindly separated its disasters. In reality, the same severe storm that inundates a neighborhood frequently severs its power lines, and the two hazards interact with human physiology and healthcare infrastructure in overlapping ways. Flooding can trigger acute psychological stress, physical exertion during evacuation and cleanup, exposure to cold water, and disruption of medication supplies. Power outages disable home medical devices such as oxygen concentrators and ventilators, knock out traffic signals and emergency services, and force vulnerable people into cold or unsafe conditions. When these mechanisms operate simultaneously, the physiological and logistical stresses multiply, and the new findings suggest the resulting hospitalization risk exceeds what either hazard alone would predict.

The authors argue that their results carry direct implications for emergency management. Identifying susceptible populations, including older adults, Medicaid beneficiaries, uninsured individuals, and rural residents, allows public health agencies to prioritize outreach, backup power for electricity-dependent patients, and early prescription refills before forecasted storms. Deploying preparedness efforts within the critical time windows the study identifies, such as the first days of prolonged flooding and outages crossing the 15.3 percent coverage threshold, could mitigate a meaningful share of the excess cardiovascular burden. As climate change drives more frequent and more intense extreme weather events, the compound-hazard framing may become not just an analytical refinement but a necessity for protecting the millions of people whose hearts bear the hidden costs of a warming, stormier world.

Subject of Research: The joint effects of co-occurring floods and power outages on cardiovascular disease hospitalizations in New York State

Article Title: A dangerous combination: how co-occurring floods and blackouts increase cardiovascular hospitalizations

Article References: Chen, Y., Tangang, R., Sun, Y., Zaloom, S., Guo, L., Song, S., Noor, M. I., Friedman, S., Wang, J., Bassill, N. P., Wang, T.-S., & Lin, S. (2026). A dangerous combination: how co-occurring floods and blackouts increase cardiovascular hospitalizations. Journal of Exposure Science & Environmental Epidemiology. https://doi.org/10.1038/s41370-026-00977-1

Image Credits: AI Generated

DOI: 10.1038/s41370-026-00977-1

Keywords: flooding, power outages, cardiovascular disease, hospitalizations, extreme weather, compound hazards, environmental epidemiology, New York State, hypertension, stroke, ischemic heart disease, vulnerable populations