Analysis shows that extreme rainfall is linked to an increased risk of deaths from heart and lung disease

Extreme rainfall is associated with an increased risk of death from all causes and from heart and lung disease, according to an analysis of data from 34 countries and regions published by The BMJ.

The health effects of extreme rainfall varied depending on local climate and vegetation cover, providing a global perspective on the effect of extreme rainfall on health.

Climate change is intensifying the frequency and severity of short-term rainfall events, and emerging evidence suggests a compelling link between rainfall events and adverse health impacts, particularly the transmission of infectious diseases.

But the impact of rainfall on cardiovascular and respiratory health, and how varying rainfall intensities influence these conditions, remains understudied.

To address this, researchers examined the associations between daily rainfall (intensity, duration and frequency) and all-cause, cardiovascular and respiratory deaths.

They analyzed daily mortality data and rainfall data from 645 locations in 34 countries or regions on six continents, totaling 109,954,744 all-cause, 31,164,161 cardiovascular, and 11,817,278 respiratory deaths between 1980 and 2020.

The main measure of interest was the association between daily deaths and precipitation events with return periods (expected intervals between events) of one year, two years and five years.

Factors that could influence this association were also taken into account, such as local climate type, rainfall variability and vegetation cover.

A total of 50,913 precipitation events with a one-year return period, 8,362 events with a two-year return period, and 3,301 events with a five-year return period were identified during the study period.

Overall, at all locations, a day of extreme rainfall with a five-year return period was associated with an 8% increase in all-cause deaths, a 5% increase in cardiovascular disease deaths, and a 29% increase in respiratory deaths over a 14-year period. day period after rainfall.

Extreme rainfall events with a two-year return period were only associated with respiratory deaths, while precipitation events with a one-year return period showed no effect on cardiovascular or respiratory deaths.

Locations with lower rainfall variability or sparse vegetation cover showed a higher risk of fatalities after extreme rainfall.

Further analysis showed protective effects of moderate to heavy rainfall, possibly due to reduced air pollution and people staying indoors. But the risk of damage increased during extreme rainfall, likely due to damage to infrastructure, water pollution and exposure to harmful microorganisms.

These are observational findings, so no firm conclusions can be drawn about causality, and the authors acknowledge that the locations analyzed were mainly in East Asia, Europe and North America, and that individual factors such as age, gender, race, place of residence in urban/rural, etc. or specific clinical settings were not captured.

However, they say these findings underscore the need for coordinated public health strategies to mitigate the broad health impacts of extreme rainfall. “This is especially important given the established trend of increasing rainfall intensity in the short term due to climate change,” they add.

In a linked editorial, John Ji of Tsinghua University in China welcomes the research and says health professionals are ideally placed to drive climate action by educating patients about climate-related health risks and promoting resilience within communities.

But despite the clear science, he acknowledges that climate action remains difficult.

“People often forget the lessons of scarcity in times of abundance – a risky form of climate change amnesia,” he notes. “The stakes are way too high, because when it rains, it pours – and in this era of escalating climate extremes, it will rain harder than ever before.”