Extreme temperatures during heat waves and cold spells may increase the risk of dying prematurely of heart disease, according to new Australian research published in an American Heart Association journal.

"The findings are important because of how the body responds to temperate extremes, the growing obesity trend and the Earth's climate changes," said the study's lead author, Cunrui Huang of Queensland University of Technology (QUT) in Brisbane.

Researchers compared data on daily temperatures between 1996 and 2004 with documented cardiovascular-related deaths for the same period.

For the purposes of the study, 11.7 C was considered a cold spell, while 29.2 C was characterized as a heat wave.

For every one million people there were 72 so-called years
of life lost - measured against life expectancy - due to cardiovascular disease, the study found.

The risk of premature CVD death was even higher when extreme heat was sustained for two or more days, the researchers found.

This might be due to greater strain on the heart, co-author Prof. Adrian G. Barnett said, citing previous research that has shown exposure to extreme temperatures can trigger changes in blood pressure, blood thickness, cholesterol and heart rate.