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An international study led by Helmholtz Munich investigates the health consequences of heavy rainfall events. Researchers analyzed the relationship between precipitation patterns and mortality rates at 645 locations across 34 countries from 1980 to 2020. The key finding: Extremely heavy rainfall, which occurs approximately every five years, significantly increases the risk of death, particularly among individuals with cardiovascular and respiratory diseases. The impacts, however, vary greatly by region and depend on local climate and environmental conditions.
“From East Asia, it was already known that extreme rain events have a strong impact on human health,” says Dr. Alexandra Schneider, Deputy Director of the Institute of Epidemiology and Head of the Environmental Risks research group at Helmholtz Munich: “With our current study, we wanted to investigate the global impacts of extreme rainfall events on health.” The team analyzed extensive data covering four decades and a wide geographical spread. “To examine the precise effects of heavy rain on mortality, we differentiated the rainfall events by their so-called return periods — the statistical frequency of such extreme events — and analyzed their impact on various health risks,” Schneider explains.
Extreme Rain Disrupts Medical Treatment and Leads to Stress
The detailed insights into the connections between extreme weather events and health consequences revealed: The data show a significant increase in mortality rates within a 14-day lag period associated with extreme rainfall, which statistically occurs about every five years. “In addition to the increase in general mortality, the negative effects of these extreme weather events were particularly evident in people with cardiovascular and respiratory diseases,” says Dr. Cheng He, lead author of the study and a scientist at Helmholtz Munich: “The health risks from extremely heavy rain can arise from medical treatments being disrupted, medications being unavailable, or affected individuals suffering from severe psychological stress. Airborne pathogens, facilitated by high humidity, are also a possible explanation.”
On the other hand, the research team observed protective effects on people’s health during comparatively moderate rainfall events with a return period of one to two years. These may be due to improved air quality and reduced air temperatures following the precipitation. The study also highlights the importance of regional factors that modify the impacts of extreme rainfall on health: climate zone, vegetation coverage, and variability in daily precipitation of each city.
Minimizing Health Risks From Heavy Rain
Given the clear results of the study, political action is essential, says Prof. Annette Peters, Director of the Institute of Epidemiology: “In light of climate change and more frequent extreme rainfall events, we need robust health prevention strategies and adaptation measures worldwide, particularly focusing on improving infrastructure and strengthening health systems in the most affected regions.” The implementation of early warning systems for extreme weather events and the promotion of green infrastructure in urban areas could also help minimize the health risks caused by heavy rainfall. “It’s not just about responding to emergencies, but proactively taking measures to protect the population from the foreseeable consequences of climate change,” says Peters: “It’s about saving lives.”