Jim Kling

May 27, 2015

DENVER — Regular aspirin use is associated with a slowing of the progression of subclinical emphysema, according to an observational study that tracked the condition using CT.

If these results are confirmed in a prospective study, aspirin would be the only known treatment to counter emphysema.

"There are a number of animal studies showing that endothelial damage contributes to the development of emphysema, and there are lung biopsies in humans showing areas of emphysema where the capillaries are destroyed," said Carrie Aaron, MD, from Columbia University Medical Center in New York City.

However, it is unclear whether this is related to "the destruction of the entire alveolar space that includes the capillaries, or whether those problems in the capillaries came first," she told Medscape Medical News here at the American Thoracic Society 2015 International Conference.

The researchers reasoned that aspirin might counter emphysema by inhibiting platelet activation, reducing inflammation, or altering blood flow in pulmonary capillaries.

Their work grew out of the ongoing Multi-Ethnic Study of Atherosclerosis (MESA) study, which involves more than 6000 patients and was designed to reveal the characteristics of subclinical cardiovascular disease and the risk factors associated with disease progression.

MESA-Lung Study

For the MESA-Lung study, Dr Aaron and her team evaluated 4469 men and women 45 to 84 years of age with no cardiovascular disease. Most, 55%, were current or former smokers. All the patients had undergone baseline coronary calcium CT scans, which the researchers used to determine the percentage of lung volume with emphysematous features.

During the 10-year follow-up period, participants underwent up to four CT scans, which were used to track increases in percent emphysema. Eighty-one percent of the subjects also underwent spirometry to measure expiratory airflow.

At each CT scan visit, any medication taken in the previous 2 weeks was assessed, and 921 (21%) of the participants reported using aspirin at least 3 times per week.

The reduction in the progression of percent emphysema, assessed with CT, was 0.36% lower in regular aspirin users than in nonusers over the 10-year follow-up (95% confidence interval [CI], –0.63 to –0.09; P = .008).

In a subanalysis of ever smokers, the reduction in progression was 0.37% lower in regular aspirin users (95% CI, –0.76 to 0.03; P = .07).

The results held when the researchers controlled for age, sex, race and ethnicity, cigarettes smoked per day, pack-years of smoking, and hypertension.

In participants who had a baseline FEV₁/FVC ratio — vital capacity expired in the first second of maximal expiration — below 0.7, progression was 0.93% lower in regular aspirin users than in nonusers (95% CI, –1.73 to –0.13; P = .02).

"It's really hard to say" if there's a causal effect, said Dr Aaron, pointing out that adjustment for confounders is difficult in an observational study. "I feel really confident in the results," she explained, "but what we're showing is an association."

Correlation, Not Causation

"It's early days yet, but I think there is some very promising information," said Wan-Cheng Tan, MD, from the University of British Columbia in Vancouver, Canada, who attended the presentation.

It is good to see that "something that is so widely used might help alleviate the cardiovascular side of things and the pulmonary side of things," she told Medscape Medical News.

The results are intriguing but difficult to interpret, said session moderator David Mannino, MD, from the University of Kentucky in Lexington. It could be that regular aspirin users are making conscious health choices.

"A person who takes an aspirin a day is probably doing it for health reasons," he explained. "They may also be living a healthier lifestyle. It's not a simple question of whether they're taking an aspirin a day, but whether it's a surrogate measure for other things."

Previous trials have measured aspirin use. "One might be able to interrogate some of those data and look for a signal," Dr Mannino said.

Dr Aaron, Dr Tan, and Dr Mannino have disclosed no relevant financial relationships.

American Thoracic Society (ATS) 2015 International Conference: Abstract A6354. Presented May 17, 2015.


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