The Hidden Health Costs of Climate Change

Climate change kills. Since 2000, nearly four million people worldwide have lost their lives due to floods, wildfires, heat waves, droughts, and other extreme weather events that have been linked to a steadily warming planet, according to a recent estimate in the journal Nature. That sweeping number can make it hard for any of us to grasp how the problem is touching health in our own small part of the world. Now, a new study in Nature Medicine provides some of that granular insight for people living in the U.S., exploring how climate-linked disasters affect visits to hospital emergency departments in counties nationwide, as well as related deaths in the aftermath of the disasters. The numbers, the researchers found, are troubling, with the hardest-hit communities showing mortality rates as much as 3.8 times higher than those that were less impacted.

“This could be a significant strain for hospitals and emergency departments, especially if they are damaged, lack power, or are short-staffed,” says Dr. Renee Salas, an emergency medicine physician at Massachusetts General Hospital and lead author of the study.

To conduct their work, Salas and her co-authors surveyed health records of Medicare patients in the more than 2,000 counties nationwide that had suffered one or more billion-dollar storms—measured by property loss, insurance claims, the cost of government recovery efforts, and more—from 2011 to 2016. They focused their research on Medicare patients only, for a number of reasons. People with private insurance may pick up or lose coverage as they change jobs, making for an incomplete dataset, while Medicare coverage, once begun, is typically continued for life. What’s more, senior citizens make up the population most vulnerable to death, injury, or illness related to climate change. Finally, Medicare is taxpayer funded, and studying the health effects of climate change—and the hit on the public pocketbook that results—is important in establishing policy going forward.

“Health costs are not currently incorporated into the total economic costs of these disasters,” says Salas.

In counties that sustained the most damage from any climate-related event, emergency department use and mortality remained elevated by 2.46% and 3.04% respectively relative to the pre-disaster period for at least one week after the event, which is about 2 to 2.5 times higher than in counties that suffered less damage. Those numbers may seem relatively small. But the study found that those hospital visits and deaths remained elevated for up to six weeks, leading to a mortality rate 3 to 4 times higher than in counties that suffered less damage from the event.

Read More: Climate Change Isn’t Just a Global Threat—It’s a Public Health Emergency

While the study only looked at floods, hurricanes, severe storms, and winter storms, acute health problems—like smoke inhalation from wildfires, dehydration, or heat stroke from soaring temperatures—often lead to the greatest number of immediate visits to emergency departments or deaths for climate-related disasters. But other kinds of harm played out more slowly. Contaminated water or mold-related infections can damage health, as can loss of power that cuts off air conditioning and such essential health devices as CPAP machines. Closures of hospitals and the inability to access needed medicines may play a role too.

“People are likely to be harmed over the longer term by the things the extreme weather event caused,” says Salas. Most of the time, she adds, reports of deaths and injuries do not consider “the long tails these events appear to be having on some of the most vulnerable.”

The climate events themselves can have their own kind of long tails. Wildfires and droughts were not examined in the study as they tend to last about 200 to 300 days, likely causing elevated sickness and injury different from the events in this study. As time goes on, those kinds of mega-crises are becoming more common. Data cited in the study and drawn from the National Centers for Environmental Information and the National Oceanic and Atmospheric Administration found that billion-dollar events account for up to 80% of all climate-related damage in the U.S. Still, the remaining 20% is not without risks. The new study, says Salas, did not provide “a complete picture of all extreme weather events.”

The world is bracing for a miserable few months when it comes to climate change. According to another study just published in Scientific Reports, a combination of greenhouse gasses and an especially intense El Niño event in the tropical Pacific Ocean will result in a 90% likelihood of record-breaking global mean surface temperatures through the end of June. The areas that are predicted to see the greatest impact are the Philippines, the Caribbean, and the Bay of Bengal region; should the heating be even worse than what the model predicts, the Amazon and Alaska will suffer acutely too. The authors of the paper warn of wildfires, cyclones, and heatwaves that will challenge the ability of local populations to adapt to or mitigate the crises—especially populations in lower income parts of the world that lack the medical infrastructure of the U.S. and other highly industrialized nations.

“Our longer-term findings are happening in a high-income country with a relatively robust health system,” says Salas. ”Death rates in low- and middle-income countries following tropical cyclones have been shown to be even greater, revealing that they may not be able to cope as well with these major climate-related disasters.”

Climate change is a planet-wide problem. It also touches the health of every one of us—nation by nation, county by county, and person by person.

Correction, March 5

The original version of this story mischaracterized several aspects of the study in Nature Medicine. The study included more than 2,000 counties, not 4,800, and the authors surveyed health records of Medicare patients, not of patients in emergency departments of major hospitals. The study did not include wildfires, drought, or excess heat. In addition, after the climate events, emergency department use and mortality remained elevated by 2.46% and 3.04% respectively, not 1.22% and 1.4%, and the risks remained 3 to 4 times higher, not 2.5 times higher, for up to six weeks. A line suggesting that follow-up data was not available for all of the counties has also been removed.