Heat related health inequalities are rising
BMJ 2023; 383 doi: https://doi.org/10.1136/bmj.p2844 (Published 01 December 2023) Cite this as: BMJ 2023;383:p2844
- Simon N Williams, lecturer, School of Psychology, Swansea University,
- Michael Marmot, professor, Institute of Health Equity and Department of Epidemiology and Public Health, University College London
This summer has been the world’s warmest, by a large margin.1 The UK experienced its hottest ever June and a record seven consecutive days of 30°C or above in September.2 In the words of UN secretary general Antonio Gutierrez, we are now in the age of “global boiling.”3
Climate change has impacts on health and health inequalities—directly and indirectly. A 2020 UCL Institute of Health Equity (IHE) report warned that climate change will widen health inequalities in the future unless we take urgent action.4 Fortunately, the action we take to reduce greenhouse gases can also promote health equity.
Extreme temperatures in either direction—below 5°C and above 25°C—are associated with the greatest risk of mortality.5 The link between cold temperatures and health inequalities is well established,6 with fuel poverty and cold homes disproportionately affecting more deprived communities. Although the link between health inequalities and excessive heat is less clear, there is growing evidence and cause for concern. We know that extreme heat and heat waves are associated with increased mortality and morbidity, and for populations less adapted to higher temperatures, mortality risk increases by 1-3% per 1°C change in high temperature.7 In the UK, heat related deaths are increasing—more than 4500 occurred in 2022 alone.5
One recent systematic review found that more deprived communities experience higher mortality risk in response to heat,8 while another review found that cities with a lower GDP have a higher heat risk, concluding that “in terms of length of life being shortened, the largest heat burden may fall on the poorest populations, who also have the least economic capacity to adapt.”7 More unequal cities (those with a higher Gini index) experience greater heat related mortality.9 A study on the 1995 Chicago heatwave found that the health effects of high heat were greater in poorer neighbourhoods with lower social capital.10 Recent evidence from the UK also suggests the unequal impact of extreme heat on mortality. One study from England and Wales found that those living in the most deprived areas had a significantly higher mortality risk.11 A study from Scotland found that among those aged 0-74, people who lived in the most deprived areas had increased heat related mortality risk compared with those in less deprived areas.12 Level of education and relative income are risk factors for heat related mortality.813 Those working outdoors, who are more likely to be from lower income or migrant backgrounds, are more likely to be affected because of increased occupational exposure to excessive heat.14
Growing evidence also suggests that extreme heat has unequal impacts on morbidity. For example, one recent study found that emergency hospital admissions owing to extreme heat were higher in more socioeconomically deprived areas of England.15 Those from the most deprived backgrounds are more likely to be admitted for heat exacerbated health conditions, including respiratory metabolic and infectious diseases, as well as accidents.15 Extreme heat and climate change also adversely affect mental health, including among those most socioeconomically disadvantaged.16
Longer term, greater exposure to UV light is another risk, particularly for countries whose populations are at higher risk of negative outcomes such as skin cancer (for example in northern Europe). Historically melanoma incidence in these populations has tended to be higher among higher socioeconomic groups (because of greater travel to low latitude countries), but strong evidence shows how people from lower income backgrounds are more likely to have a melanoma diagnosed at a more advanced stage and have poorer survival outcomes.17
The IHE report notes a host of other direct effects of climate change on health, including the adverse impacts of increasing air pollution, pollen, and extreme weather effects such as storms and floods.18 There are also indirect effects, which are also experienced unequally. For example, the impact of climate change on the prices of food, water, and energy are all likely to affect more disadvantaged populations, on both national and global levels.18
People are already starting to “feel the heat,” but some more than others. In the UK, it was recently estimated that half of the country’s housing would fail the “bedroom overheating” test.19 In lower income countries, with less advanced and equitable health systems, the rich are much better equipped to cope with rising temperatures.20 Globally, the painful irony is that those most impacted by climate change often contribute to it the least.14
What must be done?
Heat related mortality and morbidity will only get worse.21 Tackling climate change and health inequalities requires governments and society to invest in reducing air pollution, building more energy efficient homes, promoting more sustainable and healthy food, prioritising active and safe transport, creating more sustainable working conditions (eg, supporting working from home or a four day week), and city planning (eg, the 15 minute city).18
As global temperatures rise, summertime energy poverty is a growing problem in many countries, where only the wealthy can afford air conditioning.2122 But increasing air conditioning coverage is unlikely to substantially reduce heat related health inequalities and will serve only to increase greenhouse gas emissions.21
Equity and sustainability must be at the core of housing and urban planning. Evidence from the UK and internationally shows that heat related mortality is significantly higher in the “urban heat islands” of densely populated cities like London.5811 More urban and more deprived communities tend to have fewer available green spaces, which can have a cooling effect.82324 Currently, people with manual and casual occupations are nearly three times as likely to be without a garden, and individuals from some Black and ethnic minority communities are twice as likely to have minimal access to green spaces.2526 Older people in socially deprived communities are more vulnerable to heatwave related mortality—but community based interventions designed to reduce social isolation have been shown to help.27
We need to continue to invest in ways to minimise air pollution, a problem disproportionately affecting the most socioeconomically deprived.28 High pollution and high temperatures have a synergistic effect that leads to increased respiratory, circulatory, and other health problems.29
Investment in healthcare will also help. Extreme heat related mortality is higher in areas with fewer hospital beds per capita. More equitable access to better healthcare will ultimately help across a range of outcomes, from emergency admissions to earlier diagnosis and better long term survival of melanoma. Heat related health education programmes and health-warnings (including emergency alerts) need to consider issues of equity and access (for example, bridging gaps in health literacy and the digital divide).21
Promoting social equity will also help empower people to take action to reduce their contribution to climate change. Those in less deprived areas are more able to make changes to their home or shopping habits to do this.30
At the root of change needs to be a move towards “wellbeing economies” that puts health and wellbeing, of people and planet, at the heart of progress and growth.21 Ultimately, reducing health inequalities and tackling climate change are mutually beneficial goals, and this record breaking summer has been a stark reminder that the time to act on both health equity and the climate crisis is now.
Footnotes
Competing interests: SW is also a consultant for the World Health Organization, but writes here in a personal capacity as an academic lecturer, and his views are independent of WHO. MM none declared.
Provenance and peer review: commissioned; not externally peer reviewed.