Heat-induced heart disease is killing Australians

Hot weather is responsible for an average of almost 50,000 years of healthy life lost to cardiovascular disease every year among people in Australia, according to a study published in the European Heart Journal. And the news gets worse, with the study suggesting this figure could double, or even triple, by the middle of the century if we continue with the current trend of greenhouse gas emissions.

The World Meteorological Organization’s State of the Global Climate report recently confirmed that 2024 was likely the first calendar year to be more than 1.5°C above the pre-industrial era, with a global mean near-surface temperature of 1.55°C above the 1850–1900 average. Furthermore, each of the past 10 years was individually the 10 warmest years on record, and each of the past eight years has set a new record for ocean heat content. But while a hotter climate can increase the risk of dangerous weather events such as bushfires and floods, the heat itself can also be a serious burden on our health.

“When the weather is hot, our hearts have to work harder to help us cool down,” said study leader Professor Peng Bi, from The University of Adelaide. “This added pressure can be dangerous, especially for people with cardiovascular disease.

“Many of us have experienced how a warming climate can make us feel unwell, particularly during longer periods of extreme heat. However, it’s still not clear exactly how many people are living with serious heart disease or dying early because of higher temperatures, and we need to understand how this burden will increase in the future.”

To calculate the current impact of high temperatures, Bi and his fellow study authors used data from the Australian Burden of Disease Database on illness or death caused by cardiovascular disease between 2003 and 2018. Then they used a statistical model to calculate how much cardiovascular disease or death can be attributed to hot weather in different parts of Australia and the country as a whole.

Using a measure called disability-adjusted life years (DALYs), which quantifies the number of years of healthy life lost through either illness or death, the researchers found that there was an average of 49,483 years of healthy life lost annually to cardiovascular disease caused by hot weather, equating to around 7.3% of the total burden due to illness and death from cardiovascular disease. Most of these years were lost due to death, rather than illness.

The researchers then used their model to look at the likely impact of climate change driven by greenhouse gas emissions in the future. They used two of the climate change scenarios outlined by the Intergovernmental Panel on Climate Change: a scenario where emissions stabilise (Representative Concentration Pathway 4.5 or RCP4.5) and a scenario with continually rising emissions (RCP8.5). They also looked at the impact of population growth and how people might adapt to cope with higher temperatures.

The model shows that by 2030, the number of DALYs lost due to cardiovascular disease caused by hot weather will increase by 83.5%, reaching 90,779.7 DALYs, under the RCP4.5 scenario. By 2050, this number is expected to rise further to 139,828.9 DALYs, a 182.6% increase. Under the more severe RCP8.5 scenario, the DALYs are projected to increase by 92.7% to 95,343.0 DALYs in 2030 and by 225.6% to 161,095.1 in 2050.

“This study combines several key factors — climate change, population shifts and adaptation strategies — to give a full picture of the disease burden across Australia,” Bi said.

“Predicting future disease burden always comes with some uncertainty, and our models rely on assumptions that may not capture every real-life detail. However, despite these uncertainties, the comprehensive nature of our approach makes the study especially valuable for planning future climate change adaptation and mitigation strategies.”

Bi noted that the study’s findings are likely relevant in many parts of the world — not just Australia — although the specific risks may vary depending on local climates and population demographics. The good news is that the model also shows that it would be possible to lower the impact of high temperature on cardiovascular disease with strategies that help people adapt to hotter weather.

“Our research … highlights the importance of taking precautions during hot weather, such as staying hydrated, finding cool environments and seeking medical help when needed,” he said.

“Our findings also call for urgent investment in adaptation and mitigation strategies, including urban cooling plans, public health campaigns and improved emergency responses during hot weather.”

Image credit: iStock.com/Pornpak Khunatorn