How does climate change amplify health inequities?

Climate change affects many aspects of everyday life, but some groups of people feel the impact more acutely than others. Climate shocks such as higher sustained temperatures typically compound health disparities between communities – but a more resilient and equitable health system is possible.

Extreme weather, changes in precipitation and increasing temperatures driven by climate change can diminish or harm water sources, food supply and air quality. They can also strain infrastructure beyond capacity, deplete resources, increase the risks of vector-borne diseases, and so much more.

These are just a few of the effects of climate change that can disrupt or displace entire communities. But they are not felt uniformly across all geographies, communities or even neighbourhoods, particularly when it comes to people’s health.

Figure 1: Changes in global surface temperature relative to 1850-1900

Source: IPCC

How does climate change affect the health of different communities?

Climate change amplifies many structural, social and environmental determinants of health, such as social policies, food security and pollution. These factors contribute to disproportionate climate exposure for the communities and nations that often bear minimal responsibility for causing climate change, such as historically marginalised communities in the United States.

Unequal exposure increases susceptibility to the health effects associated with climate events and further heightens related inequities.

Consider a heatwave. Greenhouse gas emissions have raised global average temperatures as well as the frequency, intensity and duration of extreme heat events (Intergovernmental Panel on Climate Change, 2021; Perkins-Kirkpatrick and Lewis, 2020).

When a heatwave sweeps across a region, it brings with it extreme temperatures that can exacerbate certain chronic conditions and cause heat-related illnesses or even fatalities. It can also be destructive to critical infrastructure, placing extra stress on the power grid or damaging roads and railways.

Socio-economic and socio-environmental factors influenced by social determinants of health can make some communities more vulnerable to heat than others within the same region. For example, lower-income households may be unable to afford air conditioning or they may have limited access to preparedness or response resources.

Further, individuals from lower-income households often rely on public transport that requires waiting outside at bus or train stops. In addition, they are more likely to work in physically demanding or outdoor jobs, further increasing their heat exposure.

Certain neighbourhoods may also be more exposed to heat, such as urban heat islands. These are densely populated areas with fewer trees, less ground cover and more concrete or asphalt surfaces that retain heat.

Urban heat islands often experience higher temperatures than surrounding areas, and a history of housing segregation and underinvestment in the United States has made it more likely that people of colour and communities on lower incomes will live in such areas.

Communities living in these neighbourhoods are also more likely to have chronic diseases that make them more susceptible to heat-related health issues. In fact, a nearly decade-long study of extreme heat days in the United States found that non-Hispanic black adults were among those who experienced higher mortality rates associated with the heat.

The Community Resilience Estimate for Heat tool developed by the US Census Bureau and Arizona State University found that nearly a quarter of the US population would be socially vulnerable amid extreme heat exposure.

Crucially, more marginalised and disadvantaged communities typically have limited access to adequate healthcare services. They may also be less able to seek care due to challenging circumstances, such as lack of financial resources or not being able to take time off work to seek care. These factors compound health issues even before a climate event occurs and can contribute to poorer health outcomes and increased costs of care.

Social vulnerabilities can also make communities less able to recover or invest in effective adaptation or mitigation measures to protect themselves from future heatwaves and other climate exposures. This serves to widen existing disparities between communities even further.

What is the burden of extreme heat on health systems?

Health systems provide baseline care to meet the existing healthcare needs of the communities that they serve and accommodate any emergency care needs that may arise. But heatwaves can damage such systems.

Extreme heat ramps up healthcare needs. And if heatwaves become increasingly frequent and ferocious, they are likely to threaten the sustainability of healthcare systems.

Heatwaves can create excess service needs in the shorter term as extreme heat can contribute to health issues such as respiratory difficulties, heat cramps, heat exhaustion and non-fatal heat stroke (Hondula et al, 2015).

This temporarily increased demand may overwhelm health systems’ resources and staffing capacity while also driving up healthcare spending, particularly within communities that are already more at risk.

For example, Mathematica’s ClimaWATCH heat vulnerability assessment tool demonstrates that healthcare spending for individuals with low incomes and resources in the United States (specifically participants in the Medicaid public health insurance programme) rises during heatwaves. This is the case even if the number of individuals using healthcare services does not increase significantly.

Figure 2: Heat vulnerability index, United States, 2019

Source: ClimaWATCH

Analysis using the tool suggests that the state of Arizona spent an additional $514 million in healthcare services to treat all non-poisonous causes (for example, respiratory, circulatory and endocrine disorders) during heatwaves in 2020 alone, despite no significant spike in use rates.

This indicates that extreme heat can complicate existing health issues, making it necessary to have more complex and costly care. In fact, ClimaWATCH also shows that the excess cost to treat an individual with any existing health condition is nine times largerthan treating someone without a health condition.

The figure is up to five times larger among people with disabilities (compared with all adults). This further demonstrates that inequities exist even within an already disadvantaged population.

Climate stressors – such as higher sustained temperatures – can also contribute to increased demand for healthcare services over time. This can change the overall profile of the baseline care required in such a way that may stretch the health system’s resources and overburden staff in an unsustainable manner.

Why is a resilient health system so critical for health equity?

A resilient health system plays a crucial role in promoting health equity by ensuring sustainable care for disadvantaged communities, especially when affected by climate change.

Treating shocks brought about by climate-induced demand – for example, during an event like a heatwave – is resource-intensive and adds pressure to already overburdened health systems.

Sustained higher demand for services makes it increasingly difficult for health systems to be able to avoid interruptions to care, to maintain the quality of baseline or emergency care, or to guarantee provision of care at all. It runs the risk of insufficient resources, financial insolvency, inefficient practices and more.

These silent pressures diminish health systems’ resilience and their ability to provide reliably and sustainably for the communities in need of their services. As a result, a critical first line of response to protect people’s health and wellbeing amid climate change is at risk, and the most susceptible populations are likely to feel that burden more profoundly.

In fact, forthcoming analysis at Mathematica finds that the effect of heat on health in communities at higher risk to any natural hazard is magnified nine times. A non-resilient health system simply compounds existing structural and social inequities.

What could a more resilient and equitable health system look like – and how can it be supported?

A health system that could remain resilient and continue to provide equitable care amid a changing climate is possible. To understand how, we need to consider the ways in which climate change affects both the health system itself and the communities it serves.

This will help to plan and design more equitable policies and practices, which can be supported through:

Data

Health systems can leverage various technologies and data analytics tools – such as Mathematica's ClimaWATCH, Esri’s heat vulnerability tool, the National Institute for Occupational Safety and Health’s heat safety tool app, and more – to gain insights that can inform decision-making.

These tools assist in predictive modelling, enabling tailored scenario planning and immediate disaster response. By analysing local vulnerability assessments, health systems can pinpoint sources of inequity and allocate resources to address them effectively.

Collaboration

Health systems would benefit from engaging and collaborating more with the communities that they serve. Working directly with the communities that feel the effects of climate change most acutely can help to develop an understanding of evolving needs based on lived experience. This can also facilitate meeting those needs with equitable solutions that address the unique intricacies that each local community faces.

To foster resilience, health systems might also consider partnering with other agencies or organisations to explore what climate actions they have successfully taken. They can learn from each other and extend their capacity and access to resources to improve responses to service demands that may arise due to a climate shock or stressor.

Flexibility

To remain resilient and provide equitable services, health systems should strive to maintain a degree of flexibility in their practices. The data they collect through any assessments that they conduct and the lessons they learn from their collaborative partners and engaged communities will support dynamic decision-making.

Health systems can make necessary adjustments based on what they learn to ensure that their services remain sustainable regardless of how the climate around them may change.

As climate change exerts a far-reaching influence on so many aspects of daily life, it has the power to exacerbate existing vulnerabilities and health disparities. By looking to the evidence and working together, we can bolster more equitable communities and systems that can remain resilient amid a changing climate.

Where can I find out more?

Addressing the harmful effects of climate change on extreme heat and human health: Mathematica podcast episode with Don Berwick (National Academy of Medicine’s Climate Collaborative), Tom DiLiberto (National Oceanic and Atmospheric Administration) and Aparna Keshaviah (Mathematica).
Anticipatory migration responses to rural climate shocks: Article by Esteban Quiñones, Jenna Nobles, Fernando Riosmena and Raphael Nawrotzki.
Taking action to advance health equity: Mathematica blog by So O'Neil and Deliya Banda Wesley.
Impact of extreme temperatures on emergency hospital admissions by age and socio-economic deprivation in England: Article in Social Science and Medicine by Dheeya Rizmie, Laure de Preux, Marisa Miraldo and Rifat Atun.
Climate Impact Lab.