Heat waves and cold spells cut life expectancy

02 October, 2012

Brisbane people collectively lost 45 years of life each day the temperature was 32 degrees, a new analysis of an eight-year period of mean daily temperature and deaths from cardiovascular disease by QUT public health researchers has found.

Associate Professor Adrian Barnett, from QUT's School of Public Health and Institute of Health and Biomedical Innovation said the research team also found that cold temperatures were associated with a higher daily death rate - temperatures below 11 degrees caused the collective loss of 31 years of life per day.

Professor Barnett and his research team collected data on daily temperatures in Brisbane between 1996 and 2004 and compared them to documented cardiovascular-related deaths for the same period.

"We used the first percentile of temperature at 12 degrees to represent a cold day and the 99th percentile at 29 degrees to represent a hot day," Professor Barnett said.

"We found the greatest effect of heat occurred on the first day of exposure then decreased rapidly whereas cold effects lasted longer, peaked two days after exposure and then declined slightly with a delayed effect even after 10 days.

"Understanding the lag time between temperature exposure and years of life lost is important for health care providers to develop response plans for extreme temperature events."

Professor Barnett said it was the first study to examine the effects of daily average temperature and "years of life lost" due to cardiovascular disease.

"Years of life lost are a useful measure for assessing the preventable loss of life years because it gives greater weight to deaths of younger people," he said.

"If we understand how temperature exposure impacts on years of life lost it will help us rank the health risks against other exposures."

He said the extra deaths could be attributable to several factors including that people with underlying cardiovascular conditions became exhausted due to the sustained strain of getting blood to the skin surface to cool it in hot weather and to circulate blood through constricted blood vessels in cold.

"Other factors could be our emergency medical services become overstretched in severe weather and ambulances take longer to arrive," Professor Barnett said.

This study is one of a series of weather effects on health in response to the growing interest in the future impacts of climate change on people's health and wellbeing carried out at QUT.

"These findings have implications for the way we build houses in the future to achieve better climate control to help mitigate the effects of the expected extremes of temperature that climate change brings," Professor Barnett said.