Who is at risk of death due to extreme heat and cold?

New York, April 14: While extreme cold increases mortality risks for people with cardiovascular and respiratory diseases, extreme heat is risky for people with renal diseases, new research suggests.

The findings, published in the journal Risk Analysis, suggest that heat and cold waves affect people with certain health conditions differently, highlighting the need for tailored public service risk communication.

For the study, the researchers gathered extreme temperature data and compared it to deaths in the Minneapolis-St. Paul Metropolitan area -- known as the Twin Cities of Minnesota in the US -- between 1998 and 2014 and emergency department visits from 2005 to 2014.

"We analysed the data from Twin Cities, Minnesota, in the US, and found patterns with universal validity across the globe," said Matteo Convertino, Associate Professor of Hokkaido University in Japan who led the study.

While well known that extreme weather can be dangerous, not enough analysis has been done to compare specific temperatures against deaths and disease to know when public service messaging will be most effective.

Convertino teamed up with the University of Minnesota Twin Cities and the Minnesota Department of Health to determine which critical temperatures should trigger critical public health warnings.

The Twin Cities are known for their harsh winters and hot, humid summers.

The team found that the relative risk for mortality and morbidity increased generally with more extreme temperatures, but that at-risk populations were affected differently depending on their health conditions.

Risk for people with cardiovascular disease or respiratory illness increased in the winter, but not significantly in the summer, which was the opposite for people with renal diseases, the findings showed.

Diabetics showed no clear response to extreme temperature, the study said.

They also found that percentile-based temperature thresholds and heat index are more appropriate than absolute temperatures for determining when to initiate emergency risk communications.

"Considering climate variability over space and time, tailored emergency risk communication programmes are extremely important for informing the general public about potential health risks, such as severe heat waves or cold snaps, and how individuals can protect themselves," Convertino said.

"Our model can determine such temperature thresholds to start risk communications, which is important for saving human lives," he added.