Extreme heat linked to increased cardiovascular disease burden in Australia

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 research published in the European Heart Journal today (Monday). This equates to around 7.3% of the total burden due to illness and death from cardiovascular disease.

The study also suggests that 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 authors of the study note that since the risk of cardiovascular disease increases with higher temperatures, their findings are also relevant to people around the world.

The research was led by Peng Bi, Professor of Public Health and Environmental Medicine at the University of Adelaide, Australia.

When the weather is hot, our hearts have to work harder to help us cool down. 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."

Peng Bi, Professor of Public Health and Environmental Medicine, University of Adelaide, Australia

The researchers used a measure, called disability-adjusted life years (DALYs), which quantifies the number of years of healthy life lost through either illness or death.

To calculate the current impact of high temperatures, the researchers 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.

This showed that there was an average of 49,483 years of healthy life lost annually to cardiovascular disease caused by hot weather. 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.

Professor Bi said: "This study combines several key factors – climate change, population shifts, and adaptation strategies – to give a full picture of the disease burden across Australia. This makes our study one of the first of its kind globally. 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.

"Although our study is focused on Australia, the fundamental link between higher temperatures and increased cardiovascular risk has been documented globally. While the specific risks may vary depending on local climates, population demographics and levels of adaptation, the overall trend – that higher temperatures lead to more cardiovascular disease burden – is likely relevant in many parts of the world."

The model also shows that it would be possible to drastically lower the impact of high temperature on cardiovascular disease with strategies that help people adapt to hotter weather.

Professor Bi adds: "Our research shows that as climate change brings more frequent and intense heat, the risks associated with higher temperatures are likely to increase, especially for vulnerable groups. It highlights the importance of taking precautions during hot weather, such as staying hydrated, finding cool environments and seeking medical help when needed.

"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."