Air pollution, asthma-related event link weakened by inhaled corticosteroid use
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Key takeaways:
- With a PM2.5 rise of 10 µg/m3, veterans without inhaled corticosteroid use faced an increase in the odds for an asthma event 2 days later.
- Prospective research is required to confirm study findings.
Veterans using inhaled corticosteroids did not face increased odds for an asthma-related health care event after short-term fine particulate matter rises, according to a research letter.
“For patients with mild asthma, it’s important that they be prescribed inhaled corticosteroids as part of their treatment regimen,” Tianshi David Wu, MD, MHS, assistant professor of pulmonary and critical care medicine at Baylor College of Medicine, told Healio.
“There are now strong data that folks with mild asthma who are only given an albuterol inhaler do worse than those who receive inhaled steroids, particularly in comparison to patients who use steroids as-needed as part of a formoterol-containing combination inhaler,” Wu said.
In a case-crossover study published in American Journal of Respiratory and Critical Care Medicine, Wu and colleagues assessed 16,105 adult veterans (mean age, 56 years; 75% men) with an acute asthma-related health care event (ED visit or hospitalization) receiving regular care from the U.S. Veterans Health Administration between January 2015 and December 2019 to determine how the link between PM2.5 and acute asthma events changes with inhaled corticosteroid (ICS) use.
“Exposure to air pollution has been consistently linked to asthma flares, and because brief increases in steroids are used to treat asthma flares, we thought it was plausible that inhaled steroids might help prevent air pollution-induced worsening of asthma,” Wu told Healio.
This has been suggested in studies with pediatric patients, Wu continued, but has not been found in adult patients.
Researchers found each patient’s daily exposure to PM2.5 using their home address and the U.S. Environmental Protection Agency’s Downscaler Model.
Within the study population, 9,874 adults (61%; mean age, 57.6 years; 1.2% with prior-year exacerbation) used ICS-containing therapies in the past year, whereas the remaining 6,231 adults (39%; mean age, 53.5 years; 0.2% with prior-year exacerbation) did not have ICS use.
In the group of adults with no ICS use, researchers observed a link between an increased PM2.5 concentration and an elevated likelihood for an acute asthma event at 2- through 5-day lags.
With a PM2.5 rise of 10 µg/m3, those without ICS use faced an increase in the odds for an asthma event 2 days later by 10% (OR = 1.1; 95% CI, 1.03-1.18), whereas the odds did not differ for those with ICS use because of a significant effect modification at 2- and 3-day lags, according to researchers.
ICS use also modified the link between PM2.5 and acute asthma events at a 5-day lag when limiting the group to only those with ICS use within 90 days.
Lastly, ICS’s modification to this relationship grew stronger in two characteristic subgroups: urban settings and ever smoking status.
“Because our study was retrospective and only used data from one population, additional studies are needed before making any type of confident conclusions,” Wu told Healio. “A prospective study designed specifically to test this question is now needed.”