The number of older Americans who go to a hospital emergency room for breathing difficulties related to asthma and chronic obstructive pulmonary disease (COPD) increases on the day before a major thunderstorm, according to a study published online recently in JAMA Internal Medicine.
Each year, on average, about 3,700 visits to hospital emergency rooms for respiratory problems by people aged 65 and older can be attributed to thunderstorms, the study estimates.
That’s not a trivial number. And it’s likely to grow. As the study’s authors point out, global warming is expected to increase the number of severe thunderstorms in the United States in the coming years.
This is not the first evidence of the phenomenon that has been dubbed “thunderstorm asthma.” Several places — most notably, Melbourne, Australia, in 2016 — have reported rare outbreaks of asthma in the immediate aftermath of a thunderstorm. The outbreaks are sometimes so large that they’ve overwhelmed the local health care system. They’ve also led to deaths.
Events on that scale have not been reported in the United States, but the authors of the current study — a team led by economist Eric Zou of the University of Oregon — were curious to see what happens regarding respiratory illnesses in the U.S. during the days surrounding a thunderstorm. They focused on older adults on Medicare (those aged 65 and up) because of their detailed health records.
For the study, Zou and his colleagues used two sets of data: 1) health information collected from 46.5 million Medicare beneficiaries during the period 1999-2012 and 2) weather data amassed by the National Oceanic and Atmospheric Administration for all 3,127 U.S. counties during those same years. The data revealed more than 22 million visits to hospital emergency rooms for asthma or COPD by the Medicare beneficiaries and more than 822,000 days of thunderstorms in the various counties. (Thunderstorms were defined by the presence of lightning and rain, accompanied by strong, or above-average, winds.)
The weather data showed typical atmospheric changes before and after the thunderstorms, including a rise in temperature and in the amount of tiny particulate matter (PM 2.5) circulating in the air on the day before the storms. Pollen counts, on the other hand, as well as levels of nitrogen dioxide, ozone, sulfur dioxide and carbon monoxide, were unchanged before the storms and dropped afterward.
The Medicare data showed a modest, but statistically significant, increase in emergency department visits for both asthma and COPD in the days leading up to a thunderstorm. These visits peaked on the day before the storm, with an average of 1.8 additional hospital visits per million people.
Over the 14-year period of the study, those visits added up. The study estimates that about 52,000 extra hospital visits for asthma and COPD occurred because of the thunderstorms — or about 3,700 per year, on average.
As a “control,” the researchers also looked to see if a relationship existed between thunderstorms and either sepsis or pulmonary embolism, two medical conditions with no known relationship to stormy weather. As expected, they found none.
Limitations and implications
It’s been proposed that large “thunderstorm asthma” outbreaks, such as the 2016 one in Melbourne, result from heavy rain rupturing pollen grains, whose tiny particles then get swept up by the wind and inhaled by susceptible people, causing asthma. In the current study, however, emergency room visits for breathing problems peaked on the day before the thunderstorm. That finding suggests that the mechanism behind the thunderstorm-related U.S. cases was not rain-released pollen.
The cases were more likely linked to the rises in temperature and tiny particulates that occurred before the storms, say the study’s authors. Both factors are already known to exacerbate respiratory illnesses like asthma and COPD.
Of course, the study is observational, so it can’t prove a direct link between thunderstorms and increased incidents of hospital visits for respiratory illnesses. In addition, the study involved only older Americans, so its results may not be generalizable to younger populations or to older people living in other countries.
Still, the findings are intriguing — and yet another reminder of how global warming is impacting our health.
“While big thunderstorm asthma outbreaks are fortunately rare, we shouldn’t forget that daily, routine fluctuations in the content of the air we breathe — in this case, around/before storms — affect health in ways that can add up,” wrote pulmonologist Dr. Christopher Worsham, one of the study’s co-authors and a health services researcher at Harvard University, in a Twitter post.
“Our health is tied to our environment,” he added.
FMI: The study, which was published as a research letter, can be found on the JAMA Internal Medicine website, although the full paper is behind a paywall.