For new readers, the editors and the majority of contributors to The Medical Care Blog recently authored and signed onto a special consensus statement about climate change, labeling it the “greatest threat” to global public health. As part of the plan to publish that statement, we also declared that the drivers and health risks of climate change would be a central topic of our blog for 2024. We have published calls for clinicians to act as activists for social change, in a post titled “Don’t ‘Stay in Your Lane’”. We also reviewed and summarized the American Public Health Association’s long history of environmental and climate change advocacy and policy statements. More recently, Dr. Lisa Lines with our Healthy Intersections Podcast featured an entire episode about the carbon footprint of the US healthcare industry. Then she followed that up with a post about the connection between planetary and human health.
Climate Change
Today, I want to talk about the relationship between the changing climate, including the many, many, many cascading effects it has been linked to, and the utilization of healthcare services. I don’t want anyone to think I’m glossing over the science of climate change itself. However, I won’t attempt to lay out the evidence observing or forecasting the impact of climate change in this post. We don’t have that kind of space and that isn’t the objective today. That said, I do want to begin by identifying just a few of the key impacts that mediate the relationship of climate change to health and healthcare.
Climate change results in increased risks of extreme weather events, more frequent and severe wildfires, increased air pollution, changes in pollen levels, and the spread of vector-borne and water-related illnesses. Finally, it’s estimated that up to 250 million people will be displaced from their homes by changes to the climate by 2050. This mass displacement results from factors like sea-level rise, coastal flooding, disruption by hurricane and monsoon systems, and severe and prolonged droughts.
For more evidence-based, seminal references about the environmental risks climate change poses, consider checking out:
- The Intergovernmental Panel on Climate Change Reports;
- Including the IPCC’s Assessment Report 6, Working Group III (2022) on mitigation of climate change’s effects;
- The Environmental Protection Agency’s “Climate Change Impacts” resource page;
- NASA’s resources on Extreme Weather and Climate Change; and
- Here’s a visual representation of a timeline of the Earth’s temperature, by one of my favorite webcomics.
Climate Change’s Impact on Health
The changing climate has and will continue to affect health in a broad range of ways. In fact, there are too many examples to summarize them all here. A short summary should be enough to help contextualize the changes in healthcare seeking and access that follow. These changes are exposing more and more of the planet and the humans on it to extreme weather, rising temperatures, floods, droughts, storms and wildfires. All of these events can cause illnesses, injuries, and deaths on a massive scale. This is because high ambient temperatures result in increased rates of heat-related illnesses, respiratory and cardiovascular diseases, mental health disorders, and many other diseases.
It has and will lead to the spread of more and newer diseases, particularly those carried by insects, like ticks and mosquitos. Warming temperatures across every region on the planet mean that the habitats of these bugs have grown. Ticks carry Lyme disease, the incidence of which has doubled since 1991. Mosquito habitats are expanding rapidly, introducing new communities to one of the most dangerous and deadly vectors of diseases. Changing mosquito habitats are already responsible for introducing new diseases to the southern US, like West Nile virus, dengue, and even the first cases of locally-acquired (i.e. non-travel) malaria since 2003. It also affects the quality of the air, water, and food sources including the spread of bacteria and viruses through those avenues.
The increasing hazards associated with all of this are also contributing to the current all-time-highs in stress and other measures of poor mental health.
Climate Change Impacts on Healthcare Utilization
Utilization of healthcare is not a direct one-to-one relationship with poorer health, but there is a strong correlation of course. Most attempts to understand and predict utilization trends consider the use of care to be a combination of the need, knowledge, and literacy about that need, plus the desire to seek care, as well as access.
In the past few years, several studies have linked the effects of climate change to utilization outcomes. One very recent study in Nature Medicine attempted to characterize the impact of post-disaster healthcare utilization. The study compared Medicare beneficiaries in areas with major weather events (2011-2016) to matched-control counties during the same time periods. It showed that disasters resulted in greater ED utilization up to two weeks afterward and that mortality rates were higher for 6 weeks after each event. Counties with the most loss or damage experienced the greatest increases in ED and mortality rates compared to all affected counties, demonstrating a dose-response effect as well.
Another analysis of pediatric medical claims data, compared utilization rates during periods with extreme heat and humidity. Extreme heat was associated with higher rates of ED visits for heat-related illness; endocrine, nutritional, and metabolic diseases; and otitis media and externa, but not for all-cause admissions. This effect on heat-related illness was most pronounced for the 6-12 and 13-17 year old age groups.
Increases in Wildfires and other Respiratory Risks
A 2024 review in Healthcare demonstrated a pattern that wildfire particulate matter (PM2.5) exposure consistently results in exacerbations of pre-existing asthma and chronic obstructive pulmonary disease, with an associated escalation in healthcare utilization, including emergency department visits and hospitalizations. Children, older adults, and folks who were exposed through their jobs had the greatest risk of increased ED visits and hospitalizations related to wildfire smoke. Another study that examined the impact of a wave of wildfires in northern Israel showed that close proximity to such pollution can have prolonged effects. Indeed, the rate of hospitalizations remained elevated for two years after the period of exposure. Regardless of age, the increases in hospitalizations were most pronounced for citizens with underlying morbidities and those of low socio-economic status (even without the presence of chronic illnesses).
Of course, wildfires aren’t the only cause of increased respiratory hazards and subsequent healthcare seeking. Increased pollen levels have also been tied to increased urgent and emergency care, in-person provider visits, and provider calls/emails, using a population-based HMO database from the DC area.
Disruption of Utilization too
Changes in extreme weather can also disrupt care-seeking behavior. One study of vulnerable, HIV-clinic patients in South Florida noted spikes in ‘no show’ rates rose on days of either extreme heat or extreme precipitation events. Of course, disruption of care is not a direct increase to the cost of care or the required resource supply. Instead, it introduces greater inefficiency of delivery as available resources may increasingly be under-utilized during periods of disruption. One study of a single, major ED in Houston post-Hurricane Harvey described what happens when a hospital has 74% of inpatient beds damaged by flooding. This case study showed that their ED census decreased as a result even though the rate of ‘arrival-by-ambulance’ presentations went up, compared to historical precedent.
To Recap…
Climate Change impacts a wide range of escalating exposures that are harmful to human health. Those impacts on health lead to associated changes in healthcare utilization. This is no longer an abstraction or a hypothetical scenario. Studies are consistently tying changes in the climate to increased healthcare seeking, costs, and demand for resources.
Ben King