A new study analysing 17 years of Medicare hospitalisation records alongside major flood events has found a marked rise in specific health problems among adults aged 65 and older in the weeks following severe flooding. Researchers from the Harvard T.H. Chan School of Public Health, Ohio State University, the University of Wisconsin–Madison, and Columbia University’s Mailman School of Public Health published their findings in The Lancet Planetary Health, revealing significant increases in hospital admissions for skin diseases, nervous system conditions, and injuries or poisonings.
Unlike earlier studies, which tended to focus on single flood events or a narrow range of health outcomes, this research offers broad, generalisable insights with a focus on older populations in high-income countries. By matching Medicare data from 2000 to 2016 with satellite-based, high-resolution flood maps from the Global Flood Database, the team examined hospitalisation trends across 72 major floods, covering more than 4.5 million admissions. They calculated relative percentage changes for 13 disease categories within four weeks following flood exposure.
Their results showed an average increase in hospitalisations for skin diseases (3.1%), nervous system diseases (2.5%), musculoskeletal disorders (1.3%), and injuries or poisonings (1.1%). The analysis also uncovered disparities linked to community demographics. In areas with fewer Black residents, nervous system-related admissions rose sharply (7.6%). In contrast, in communities with larger Black populations, there were higher increases for skin diseases (6.1%) and mental health-related conditions (3.0%) during flood exposure. These differences may reflect variations in pre-existing health conditions, housing quality, emergency resource access, healthcare availability, and even potential biases in medical coding practices.
The study points out that older adults face heightened vulnerability to flood-related health risks due to factors such as weakened immune systems, limited mobility, pre-existing medical conditions like dementia, and reduced access to routine medical care. For example, skin infections may result from contact with polluted water, crowded shelters, and poor sanitation. Nervous system complications, such as seizures, could stem from traumatic brain injuries or stress-triggered episodes in those with epilepsy. Musculoskeletal injuries may arise both from direct harm during the flood and from strain incurred during post-flood clean-up, especially when care is delayed.
The authors stress that their findings should inform climate adaptation and disaster preparedness strategies. They recommend targeted outreach and evacuation planning for older adults, community-based alert systems, and ensuring hospital infrastructure remains functional during floods by relocating critical equipment above flood levels. They also highlight the potential role of mobile medical units, telemedicine, and drone technology in delivering essential supplies and guiding evacuations in real time. These measures could substantially reduce the health toll of flooding on vulnerable populations as climate change increases the frequency and severity of extreme weather events.
More information: Sarika Aggarwal et al, Severe flooding and cause-specific hospitalisation among older adults in the USA: a retrospective matched cohort analysis, The Lancet Planetary Health. DOI: 10.1016/S2542-5196(25)00132-9
Journal information: The Lancet Planetary Health Provided by Columbia University’s Mailman School of Public Health
