New research has found extremely hot and cold temperatures increase the risk of death among people with cardiovascular diseases, particularly heart failure.
An international study, published Monday in the American Heart Association journal Circulation, looked at more than 32 million cardiovascular deaths over four decades from more than two dozen countries.
It found people with heart failure experienced the most additional deaths from extreme temperatures compared to those with other heart conditions.
"The decline in cardiovascular death rates since the 1960s is a huge public health success story as cardiologists identified and addressed individual risk factors such as tobacco, physical inactivity, Type 2 diabetes, high blood pressure and others," Dr. Barrak Alahmad, a research fellow at the Harvard T.H. Chan School of Public Health and a faculty member at the College of Public Health at Kuwait University, said in a news release.
"The current challenge now is the environment and what climate change might hold for us."
The study used health data, pulled from 567 cities in 27 countries across five continents between 1979 and 2019, through the Multi-Country Multi-City Collaborative Research Network.
Researchers compared cardiovascular deaths on the hottest and coldest 2.5 per cent of days for each city with cardiovascular deaths in those same cities on days that had optimal temperatures or when death rates were lowest.
The study found that for every 1,000 cardiovascular deaths, extreme hot days accounted for 2.2 additional deaths, while extreme cold days accounted for 9.1 additional deaths.
When comparing types of heart disease, the greatest number of additional deaths were among people who had heart failure, with 2.6 and 12.8 additional deaths occurring on extreme hot and cold days respectively.
The researchers say the study is limited by the underrepresentation of South Asia, the Middle East and Africa in the data.
Dr. Haitham Khraishah, co-author of the study and a cardiovascular disease fellow at the University of Maryland School of Medicine and Medical Center, said the "progressive nature of heart failure" could leave patients more vulnerable to temperature changes.
"This is an important finding since one out of four people with heart failure are readmitted to the hospital within 30 days of discharge, and only 20 per cent of patients with heart failure survive 10 years after diagnosis," Khraishah said.
The researchers say with climate change, strategies that could reduce the impact of extreme temperatures on cardiovascular disease are needed.
