Two summers ago, in the middle of my busy shift in the emergency department, my mother called. At 85 years old and struggling with dementia, she was barely managing to live independently in the childhood home where I grew up. On this particular evening, her air conditioning (AC) had failed.
It was a bad day to lose AC. In the midst of a heat wave, the temperature in her Northern California neighborhood was 105°F and climbing. No longer able to drive, my mother was now effectively stuck in a house with an ambient temperature of 95°F. By the time I reached her several hours later, I found her listless on the couch, a fan circling uselessly in front of her.
Fast forward to last month’s record-setting heat wave in Europe, which coincided with an astonishing 5,700 excess deaths in France. While authorities say the deaths were due to “all causes” and not clearly linked to heat, the vast majority were among the elderly and a third in people’s homes. Why such startling statistics? Only a quarter of French households have AC. When France’s heat wave hit, its citizens roasted, just like my mother in Northern California.
All of this has me wondering: physicians prescribe statins and anti-hypertensives to ward off cardiovascular disease, and inhalers to prevent asthma exacerbations; why not AC, covered by insurance, to prevent heat-related mortality?
Too Hot to Handle
For humans, there’s a “just right” Goldilocks temperature zone above which morbidity and mortality begin to sharply increase. As temperatures rise, some individuals develop heat stroke, which carries a mortality rate approaching 80%. Many others experience worsening of their chronic diseases — especially diabetes, dementia, and cardiovascular, lung, and kidney disease — which tend to worsen in extreme heat, sometimes proving fatal. Since heat waves have been increasing in frequency, intensity, and duration for several decades, it’s hardly surprising that U.S. heat-related mortality jumped 117% between 1999 and 2023.
And, like so many things, heat risk isn’t distributed evenly. Some individuals, like the very young, the elderly, pregnant women, and those with chronic diseases, are more susceptible due to physiologic factors. Others are vulnerable due to environmental factors. Low income households, for instance, tend to be higher risk: a zip code in New York’s East Harlem is twice as vulnerable to heat-related morbidity as a zip code three blocks away on the Upper East Side. Individuals of marginalized ethnic and racial groups are also at particularly high risk of heat-related illness.
A Breath of Fresh Air
Enter air conditioning. Invented in 1902, AC began appearing first in public buildings and then in people’s homes. Today, 88% of all U.S. households have it. The problem with AC is that it’s an environmental scourge. For one, most AC units rely on refrigerants that are powerful greenhouse gases. AC also consumes a ton of energy: it’s responsible for 19% of Americans’ home electricity consumption. Plus, AC can worsen both the “urban heat island effect” and outdoor air quality.
But it also works. As a preventive health tool, AC is transformative, especially in high-risk individuals. By one estimate, the likelihood of prematurely dying on a scorching day dropped an extraordinary 80% in the U.S. between 1990 and 2004, due almost entirely to the widespread adoption of residential AC. In 2019 alone, AC prevented an estimated 47,800 heat-related deaths in elderly Americans. Ownership and usage of AC is also associated with a significant drop in hospitalizations. Even access to an air-conditioned environment for part of the day is protective, trumping other mitigation strategies such as fans and frequent showers. In short, AC is unparalleled in its ability to prevent heat-related morbidity and mortality.
You might be curious about the roughly 35 million Americans who don’t have air-conditioning in their home. About a third are Black or Hispanic. In addition, 17% of lower-income households report no access to AC, including 7% in regions with above-average temperatures.
A Prescription for Relief
So where does all this leave us? As a physician who cares deeply about environmental degradation, I’ve come to the opinion that it’s time for physicians and health systems to start prescribing air conditioning. My hope is that AC will become less environmentally destructive and that we will eventually see cities redesigned to sustainably protect citizens. But people are dying today from extreme heat. The time to act is now.
The good news is that it’s getting easier to identify high-risk patients. Many health systems’ recent implementation of social health screening means that physicians increasingly know which patients either lack AC or can’t afford to turn it on. The Census Bureau recently published Local Air Conditioning Estimates, which offer detailed information about AC access. And the Energy Information Administration has begun publishing statistics on utility disconnections.
In the past few years, innovative programs aimed at increasing vulnerable patients’ access to AC have emerged. In 2023, Boston Medical Center launched a Clean Power Prescription program, designed to address energy insecurity by transferring credits from its own solar energy generation to high-risk patients’ utility bills. Thirteen states now have a coverage benefit under Medicaid that allows physicians to prescribe AC units to highly-vulnerable patients. Unfortunately, such programs are few and far between. Broader access is essential: both Medicaid and Medicare coverage in all 50 states should offer an AC coverage benefit to beneficiaries.
My mother survived that summer day 2 years ago. We moved her to an air-conditioned hotel room until her AC was repaired, and we devised a plan to keep her safe during future heat waves. We were lucky. Too many others haven’t been this summer.
As heat waves continue to accelerate, heat-related illness is fast becoming a regularly recurring seasonal disease. But it’s a preventable illness. Physicians and insurers need to start treating it like one.
This perspective is the author’s alone and does not necessarily reflect that of any institutions or companies with which she is affiliated.
