Extreme temperatures during hot or cold spells may increase the risk of premature death from heart disease, a new Australian study says.
The risk of heart disease-related death is higher during heat waves than during cold snaps, according to the study, which was published Sept. 18 in the journal Circulation: Cardiovascular Quality and Outcomes.
These new findings are important in light of growing rates of obesity and climate change, said lead researcher 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 journal news release. "That could increase the future disease burden of extreme temperatures."
Researchers compared daily temperatures in Brisbane between 1996 and 2004 with years of life lost to heart disease during the same period. Years of life lost measures premature death by estimating years of life lost according to average life expectancy.
The average daily temperature during that time was 68.9 degrees Fahrenheit. The coldest 1 percent of days (53 degrees) were characterized as cold spells and the hottest 1 percent (84.5 degrees) as heat waves.
The researchers found that 72 years of life per 1 million people were lost each day because of heart disease. The risk of premature death from heart disease was highest when extreme heat lasted for two or more days.
Previous research has shown that extreme temperatures can trigger changes in blood pressure, blood thickness, cholesterol and heart rate, according to the news release.
Study co-author Adrian Barnett, associate professor of biostatistics at the university, said the researchers have a theory as to why deaths from extreme heat outrun 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.
While the study uncovered an association between temperature and heart disease-linked fatalities, it didn't establish a causal relationship.