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Climate change and cardiovascular disease are intrinsically linked, and more needs to be done to combat this existential threat to human health.
It was during the devastating 2019–20 bushfires, when the sky was black with smoke, and hazardous air quality meant keeping my young children indoors, that I was prompted to investigate the effects of climate change on cardiovascular disease (CVD).
From being “deeply concerned” about climate change, I became “absolutely terrified”.
Burning fossil fuels (coal, oil and gas) is the main driver of global warming, which increases extreme weather events (heat/heatwaves, bushfires, floods, cyclones, dust storms); air pollution; food and water insecurity; impacts the spread of vector borne illnesses; and disrupts health care delivery, all of which, directly or indirectly, increase the risk of CVD.
Heat
Heat kills — it’s the silent assassin of climate change. The primary cause of death during a heatwave is from cardiovascular events. Extreme heat increases deaths and hospitalisations from CVD. Heatwaves are associated with an 11% increase in cardiovascular deaths, and the more intense the heatwave, the greater the risk. Multiple Australian and New Zealand studies have shown increased rates of ischaemic heart disease (IHD) deaths and hospitalisations with extreme heat. With global warming, population growth, and an ageing population, rates of IHD — currently the leading cause of death in Australia — will continue to increase. A recent paper found that high temperatures accounted for 7.3% of CVD morbidity and mortality in Australia; by 2050 this is expected to double with population growth and no adaptation.
Air pollution
Air pollution is the fourth highest modifiable risk factor for CVD, contributing to more CVD deaths and disability-adjusted life years than smoking. Additionally , there is extensive evidence linking air pollution to multiple cardiovascular conditions including IHD, heart failure and arrhythmias.
Climate change and air pollution are interlinked. The major driver of air pollution, fossil fuel combustion, is also a source of greenhouse gas emissions (GHGe), which increases climate change; while extreme weather events, such as bushfires, made worse by climate change, increase air pollution, creating a vicious cycle.
The increase in frequency and severity of bushfires, and the associated bushfire smoke is associated with increased IHD morbidity and mortality. Australia’s 2019–20 bushfire smoke contributed to 1124 CVD hospitalisations. A separate study has estimated that the increase in daily particulate matter less than 2.5 µm in diameter (PM2.5) is associated with an increased daily CVD mortality by 4.5%.
Extreme weather events have synergistic effects: extreme heat amplifies the CVD mortality/morbidity effects of wildfire smoke.
Finally, climate change worsens mental health, and poor mental health increases CVD.Extreme weather events can also cause Takotsubo, a type of heart failure often triggered by emotional stress, for example someone losing their home after a flood.
Cardiac co-benefits of climate change mitigation
There are measures that benefit both our hearts and the planet.
Plant-based diets
Beef production constitutes more than 50% of agriculture’s GHGe, and is the number one cause of deforestation in Australia. High red/processed meat and dairy consumption contributed to 12 100 deaths in Australia in 2021. These meats increase CVD risk and mortality, while plant-based foods reduce this risk.The Mediterranean, pescatarian, and vegetarian diets lower GHGe and CVD risk, while omnivorous diets increase emissions.
Increase active and green transport
Road transport relies heavily on fossil fuels and contributes significant GHGe. Traffic-related air pollution is associated with increased CVD deaths and myocardial infarctions. In Australia, motor vehicle emissions are likely to contribute to more than 10 000 premature deaths and 11 000 CVD hospitalisations annually. Increasing active transport, such as walking, cycling and taking public transport would reduce emissions from private motor vehicle use and provide significant health benefits, including lowering CVD.
Transitioning to electric vehicles for personal and public transport and minimising idling of combustion-engine vehicles will help reduce traffic-related air pollution and improve health outcomes.
Change to renewable energy sources (eg, solar and wind)
Approximately 8.3 million people globally die each year due to outdoor air pollution from PM2.5 and ozone alone; 5.1 million of these deaths were linked to fossil fuels, 2.54 million from IHD. Changing to renewable energy sources reduces GHGe, air pollution and its adverse health effects, including CVD deaths and hospitalisations. Shutting a US coal coking plant led to a lasting decline in local cardiovascular emergency department visits.
Increase green spaces, reduce deforestation
Trees and forests are important carbon sinks, reduce greenhouse gases, improve air quality, and are biodiversity reservoirs. Increasing green spaces and spending more time in nature has multiple health benefits, including reducing CVD, cancer and mental illness. Trees also provide shade, reduce the urban heat island effect and heat-related illness.
Practise health care sustainability
While climate change contributes to increasing health care demands, the health care sector itself accounts for about 5–7% of Australia’s GHGe.A recent government and medical college endorsed joint statement iterated: we need to prioritise prevention, to improve health while reducing health care demand and associated emissions; minimise potentially harmful and wasteful care (which accounts for around 30% of clinical care emissions); and minimise emissions associated with high-value care delivery.
Finally, “we must cure the sickness of climate inaction.” Doctors pledge to “do no harm” — we should all be involved in battling climate change, the biggest threat to public health. Doctors need to speak up. We can use our voice to advocate for governments to consider the enormous economic and health costs of climate change-driven extreme weather events, before approving fossil fuel projects. The $14.5 billion ($27,581/minute) in government subsidies to fossil fuel producers who are harming health, would be better spent helping the health care system decarbonise and adapt to the growing health threats of climate change.
A healthy and happy heart needs a healthy planet.
Dr Fiona Foo is a clinical and interventional cardiologist and Co-Vice Chair Doctors for the Environment Australia (DEA) NSW Committee.
The statements or opinions expressed in this article reflect the views of the authors and do not necessarily represent the official policy of the AMA, the MJA or InSight+ unless so stated.
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