Ellen Phiddian
Cosmos science journalist
Floods are at their deadliest a few weeks after the disaster, according to a new study.
The research, published in the British Medical Journal, finds that mortality risk increases by 2.1% in communities up to 60 days after a flood has been through.
This includes deaths caused by cardiovascular and respiratory issues.
“The mortality risks associated with floods appear about 10 days after the flood, and peak at about 25 days after flood,” says co-author Professor Yuming Guo, a researcher in planetary health at Monash University.
“In general, the risk disappears after 60 days.”
Guo and colleagues analysed data from 761 communities in 35 countries, all of which experienced a flood between 2000 and 2019.
“We examined the association between floods and mortality in each community,” says Guo.
In total, the researchers reviewed 47.6 million deaths from all causes, including 11.1 million cardiovascular deaths and 4.9 million respiratory deaths.
All of these deaths increased in frequency after floods. Effects were most prominent in communities with a low socioeconomic status and a high proportion of older people.
“I am surprised that the impacts of floods on all-cause, cardiovascular and respiratory mortality can last for about 60 days. We assumed that the risks might be only about 2-3 weeks,” says Guo.
The researchers only investigated respiratory and cardiovascular deaths in detail, so cannot draw conclusions about causes of other deaths.
“In general, flooding is also related to communicable diseases, like diarrhea,” says Guo.
Australia’s mortality results were similar to the global average, with respiratory mortality particularly affected by floods.
In this study, the researchers only investigated short-term effects. But Guo says there is more research in the pipeline suggesting there might be long-term health effects too.
“Based on our other not yet published data, there are also health risks several years after the exposure to floods,” he says.
The researchers point out in their paper that floods, and their health effects, are on the increase because of climate change. Rising sea levels and increased precipitation will both cause more floods.
“Policy makers and health professionals should raise awareness of the increased mortality risk after floods to improve disaster response strategies and thereby reduce the number of avoidable deaths,” write the researchers.