Extreme temperatures during heat waves and cold spells may significantly increase the risk of premature death from heart disease, according to a new study.
However, the findings, published in the journal Circulation: Cardiovascular Quality and Outcomes, reveal that the risk of heart disease-related death is higher during heat waves than during cold spells.
The latest findings are important because of the rising rates of obesity and climate change, said lead author Cunrui Huang, of the School of Public Health and Institute of Health and Biomedical Innovation at Queensland University of Technology in Brisbane, Australia.
"With increasing rates of obesity and related conditions, including diabetes, more people will be vulnerable to extreme temperatures," Huang said in a news release. "That could increase the future disease burden of extreme temperatures."
The study compared daily temperatures in Brisbane, Australia between 1996 and 2004 with years of life lost to heart disease during the same period. Premature death, or years of life lost, was measured according to the average life expectancy.
Researchers said that Brisbane has hot, humid summers and mild, dry winters. The average daily temperature during the time the study was conducted was 68.9 degrees Fahrenheit, with the coldest 1 percent of the days being 53 degrees and the hottest 1 percent being 84.5 degrees.
Researchers characterized the coldest 1 percent of days as cold spells and the hottest 1 percent of days at heat waves. The team found that 72 years of life per 1 million people were lost each day because of heart disease, and that the risk of heart disease-related deaths was highest when extreme heat lasted for two or more days.
Past studies found that exposure to extreme temperature can also trigger changes in blood pressure, blood thickness, cholesterol and heart rate.
Co-author, Adrian Barnett, associate professor of biostatistics at Queensland University of Technology, said that the research team has a theory as to why deaths from extreme heat occur more frequently than deaths from severe cold.
"We suspect that people take better protective actions during prolonged cold weather, which might be why we did not find as great a risk of [cardiovascular death] during cold spells," Barnett said.
Researchers noted that while the recent study found an association between temperature and heart disease-liked deaths, it did not establish a causal relationship.