ACE Inhibitors, ARBs Slow Progression of Emphysema

A study recently published in Annals of the American Thoracic Society found an association between treatment with angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs), and a reduction in percent emphysema on chest computed tomography (CT). The association was the most pronounced in former smokers.¹

The Multi-Ethnic Study of Atherosclerosis (MESA) Lung Study (ClinicalTrials.gov identifier: NCT00843271) enrolled 4472 participants, from 2004 to 2012, with a mean age of 61±10 years at baseline. Twelve percent of study participants were taking ACE inhibitors and 6% were taking an ARB at baseline; only 0.2% used both medications. The distribution of current smokers, former smokers, and never-smokers was 14%, 40%, and 46%, respectively. The effect of treatment on percent lung emphysema was monitored using chest CT; all study participants underwent baseline cardiac CT taken upon enrollment, as well as repeat scans through 2007, with a median of 3 scans over a 9.3-year follow-up period.

The study found a significant association between the use of a full dose of an ACE inhibitor or ARB and a decline in the progression of percent emphysema over 10 years compared with no ACE inhibitor or ARB use (-0.68%, 95% CI: -1.28 to -0.09%; P =.02). In participants who did not take ACE inhibitors or ARBs, the predicted mean increase in emphysema was 0.66%; in contrast, it was only 0.06% in participants who used the full dose of either treatment agent.

The effect was not as dramatic in participants taking low doses of ACE inhibitors or ARBs. The researchers reported that this group of participants “had a nonsignificantly slower rate of progression in percent emphysema over time than participants not taking an ACE inhibitor or ARB.”

When each agent was examined separately, the effect of ACE inhibitor on decline in the progression of emphysema over time was found to be positive and significant, while this association was present but not significant in the case of ARB.

Hypertension and diabetes, as well as slightly higher percent emphysema at baseline, were more frequently found in study participants taking ACE inhibitors or ARBs. Furthermore, the smoking status of participants had a profound effect on the study results.

“There were highly statistically significant associations among former smokers for doses of ACE inhibitor or ARB in addition to ARB with a consistent although nonsignificant association for ACE inhibitors,” explained researchers in their paper.

The association was not observed among participants with no smoking history, while it was present but nonsignificant for current smokers. According to spirometry results, there was no evidence of an association between ACE inhibitor or ARB dose use and change in lung function over 5 years.

The findings of this large, prospective cohort study suggest that ACE inhibitors and ARBs might have potential for clinical application in the prevention and treatment of emphysema. Study authors concluded their paper by noting that “randomized clinical trials of medications targeting the renin-angiotensin system pathway and the endothelium are warranted in emphysema to determine their potential therapeutic benefits.”