The CVD burden due to heat will grow, and certain groups are more vulnerable to dying in heatwaves, Australian research finds.
Hot weather costs Australians around 50,000 years of healthy life every year, and may soon account for more than 10% of the cardiovascular disease burden, researchers have found.
Heat accounted for 11.7 million disability-adjusted life years (DALYs) lost across the globe in 2019, according to the Global Burden of Disease study, and CVD accounted for around 18.6 million deaths in the same year.
Given Australia’s vulnerability to global warming, a team led by Professor Peng Bi from the University of Adelaide set out to quantify the high-temperature-attributable burden of CVD across the nation, in both years of life lost and years lost to disability, between 2003 and 2018.
In their study, published in the European Heart Journal, they also projected into the future under different emissions and climate change adaptation scenarios.
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Using data on CVD and temperatures across 2000 geographic areas, the team calculated an overall population-attributable fraction of CVD of 7.3%, with mortality accounting for nearly all of that burden.
The heat-attributable CVD burden was higher in the southern states, especially western NSW, western Victoria and eastern SA.
Over the next few decades, SA was projected to remain stable regardless of climate change adaptation, while the NT might go from the lowest to the highest, especially in the case of low or no adaptation.
In a “full adaptation” scenario, the overall heat-attributable CVD burden was projected to decrease. With no adaptation, it was predicted to increase to 9.1% or 10.5%, depending on level of greenhouse emissions.
“As adaptation capacity can be related to socioeconomic status, financial support for cooling and subsidies for air conditioning/electricity costs may likely benefit those with fewest resources,” the authors write.
“Furthermore, as patients with CVD are more at risk during hot weather, it is prudent for clinicians to provide practical advice relating to increasing fluid intake and plant-based diets, reducing outdoor activity levels, and guidelines for storing heat-sensitive medications.”
People with cardiovascular disease or mental health problems are at higher risk of dying from extreme heat, according to Australian research published in BMC Public Health last month.
The scoping review included 64 studies with data on 85 diseases that could lead to ED presentations, hospitalisations, ambulance callouts or deaths.
The researchers found that the highest risks of heat-related deaths were in people with mental or behavioural disorders, cardiovascular diseases, diabetes and respiratory disease.
“The majority of studies reported an increase in heat-associated hospitalisation, particularly for patients with renal disease, neurological disease, stroke, mental disorders, diabetes, and ischemic heart disease,” the paper says.
“Heat-associated ambulance callouts was prominent for patients with cardiovascular and respiratory diseases.”
Extreme heat dysregulates systemic blood flow and increases myocardial strain, blood viscosity, and total cholesterol levels, leading to coronary and cerebral thrombosis, the paper says.
And breathing hot air could trigger high respiratory ventilation rate and bronchoconstriction among people with asthma as well as in healthy people.
“Younger adults may experience high plasma-based kidney biomarkers, particularly creatinine and cystatin C, which increase the risk of kidney complications during extreme heat conditions.”
There were 354 deaths from heatwaves between 2000 and 2018.
The researchers said the eight heat vulnerability index studies included in the research focused on major cities, “making it challenging to know the extent of heat vulnerability across the non-urban parts of Australia, especially the remote and regional areas”.
“Therefore, developing national HVI mapping that includes these different geographical units will provide a better understanding of the heat vulnerability in Australia.”
