How heat waves affect our physical and mental health

With temperatures climbing to record highs in many parts of the United States, medical and city officials alike are on high alert to prevent and mitigate the toll heat waves can have on our health.

Although many may think health risks of extreme heat stop at heat stroke and exhaustion, “those are actually pretty rare,” explains Aaron Bernstein, director of The Center for Climate, Health, and the Global Environment at Harvard T.H. Chan School of Public Health and pediatrician at Boston Children’s Hospital.

In an interview with Changing America, Bernstein even classified heightened attention paid to these risks as a disservice to the public. 

While heat exhaustion and heat stroke do happen, “really what's much more important is that [heat] can make existing diseases flare,” Bernstein says. Because organs do not function as well as normal during periods of extreme heat, risks for individuals with chronic medical problems like diabetes, COPD, or heart disease spike during heat waves. 

Other vulnerable populations include older individuals — especially those over 80 — pregnant individuals, infants, outdoor workers, and those reliant on technology-dependent care, Bernstein added, as the threat of power outages often looms during intense heat. But, “heat can land you in a healthcare facility at any age,” Bernstein said. 

Urologist and pediatrician Gregory Tasian of the Children’s Hospital of Philadelphia says that the research going back to the 1970s shows that there is a higher prevalence of kidney stones in hotter areas – leading experts to dub the region the “stone belt.” A combination of high temperatures and high humidity increases risk of kidney stones.

While a heat wave may not cause a kidney stone on its own, it could contribute to the condition for people who were already at risk. When you consider periods of high temperatures, “you're likely going to have more people who what I call tip over into the stones because they have other risk factors for it,” says Tasian. This includes people who have had a history of kidney stones or have a family history of stone disease. 

Heat can also affect those with certain mental health conditions. Commonly prescribed treatments for mental health disorders, including selective serotonin reuptake inhibitors (SSRIs), can make patients sweat more, exacerbating the threat of dehydration. Heat waves have also been associated with increased rates of violent crime.

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More days of high heat can also increase the rates of mental health emergencies in hospitals. Temperature spikes across the country are associated with a rise in emergency department visits for mental health reasons, according to study results presented by Amruta Nori-Sarma of Boston University in a briefing. Heat is an external stressor that can exacerbate not only physical conditions but also mental conditions.

Heat waves – and its toll on our mental and physical health – are only becoming more frequent and intense with climate change. 

 “A child born in 2020 in the United States will experience around 35 times more dangerous heat waves, like the one that spread across most of the country in the past week or so, than a child born in the United States in the 19th century,” Bernstein said. “[This is] because of climate change, because of our reliance on fossil fuels.”

Heat-related deaths often lag from the peak of heat waves, and could happen as much as 24 hours later, says professor of global health Kristie Ebi at the University of Washington. This makes it important to pay attention during the following days. 

“It's a particular problem when temperatures do not fall as much as normal during the night,” says Ebi. “So paying attention, not just on day one. But on days two, three and four, because the accumulation of heat within the core of our bodies start affecting ourselves and our organs.” 

During the heat dome that hit the Pacific Northwest last year, there was a 69-fold increase in heat-related presentations in hospitals. Since then, local government officials in Seattle have rolled out a comprehensive heat action plan, according to Ebi, that’s been effective in informing people about oncoming heat waves and how to stay safe. However, there’s still a lot more planning that needs to be done in terms of providing services to make sure that hospitals and clinics can handle an increase in heat-related cases, Ebi added.

“Heat does not spare any part of our bodies,” Bernstein says. But understanding the combination of factors that increase a person’s vulnerability can help inform more targeted approaches to prevent hospitalizations and poor outcomes.

Part of the challenge of dealing with high temperatures is that there is no official definition of heat waves, and how a population as a whole handles higher temperatures may also depend on behavior and knowledge. Certain social factors like limited mobility, lack of access to air conditioning, and being socially isolated all need to be taken into account when identifying and protecting those most at risk, he stressed. 

“Those individuals who work in jobs that require you to be outside are going to be the most impacted and I think that certainly extends beyond kidney stones into the other effects of temperature on human health,” says Tasian. 

Being proactive and having resources in place to address the potential health consequences of heat waves before they strike is paramount. 

Taking heat alert warnings from the National Weather Service as an example, Bernstein explains, “those alerts are being given at temperatures well above when many, if not most, of the people who are vulnerable are already sick and getting hospitalized,” marking an opportunity for improvement.

Heat action plans at the local government level can include outreach to at-risk groups, Ebi tells Changing America. These include unhoused people, people with chronic conditions and pregnant people. For example, they can make sure people know where local cooling centers are to take shelter during periods of high heat.

Health systems can also leverage the information they have about at-risk patients to better enable successful heat plans, another action — deemed patient-centered climate resilience — underway by Bernstein and colleagues at the T.H. Chan School of Public Health.

When cities open cooling centers during heat waves, those who are socially isolated or people with limited mobility will likely not make the journey, again underscoring the importance of identifying at-risk members of the community beforehand. 

Both heat alerts and cooling centers are useful, but more can be done to help prevent avoidable deaths and poor outcomes reported when heat waves strike. As Nori-Sarma puts it, social ties are the best protection against adverse effects.

For example, health-outcomes-based heat warning systems tailored to a city’s geographic location offer a potential solution for some communities. This is already being tested by the Adrienne Arsht-Rockefeller Foundation Resilience Center.