Randomized Clinical Trial of Air Cleaners to Improve Indoor Air Quality and Chronic Obstructive Pulmonary Disease Health Results of the CLEAN AIR Study

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Rationale: Indoor particulate matter is associated with worse chronic obstructive pulmonary disease (COPD) outcomes. It remains unknown whether reductions of indoor pollutants improve respiratory morbidity. Objectives: To determine whether placement of active portable high-efficiency particulate air cleaners can improve respiratory morbidity in former smokers. Methods: Eligible former smokers with moderate-to-severe COPD received active or sham portable high-efficiency particulate absolute air cleaners and were followed for 6 months in this blinded randomized controlled trial. The primary outcome was 6-month change in St. George’s Respiratory Questionnaire (SGRQ). Secondary outcomes were exacerbation risk, respiratory symptoms, rescue medication use, and 6-minute-walk distance (6MWD). Intention-to-treat analysis included all subjects, and per-protocol analysis included adherent participants (greater than 80% use of air cleaner). Measurements and Main Results: A total of 116 participants were randomized, of which 84.5% completed the study. There was no statistically significant difference in total SGRQ score, but the active filter group had greater reduction in SGRQ symptom subscale (b, 27.7 [95% confidence interval (CI), 215.0 to 20.37]) and respiratory symptoms (Breathlessness, Cough, and Sputum Scale, b, 20.8 [95% CI, 21.5 to 20.1]); and lower rate of moderate exacerbations (incidence rate ratio, 0.32 [95% CI, 0.12–0.91]) and rescue medication use (incidence rate ratio, 0.54 [95% CI, 0.33–0.86]) compared with sham group (all P, 0.05). In per-protocol analysis, there was a statistically significant difference in primary outcome between the active filter versus sham group (SGRQ, b 24.76 [95% CI, 29.2 to 20.34]) and in moderate exacerbation risk, Breathlessness, Cough, and Sputum Scale, and 6MWD. Participants spending more time indoors were more likely to have treatment benefit. Conclusions: This is the first environmental intervention study conducted among former smokers with COPD showing potential health benefits of portable high-efficiency particulate absolute air cleaners, particularly among those with greater adherence and spending a greater time indoors.

Original languageEnglish (US)
Pages (from-to)421-430
Number of pages10
JournalAmerican journal of respiratory and critical care medicine
Issue number4
StatePublished - Feb 15 2022


  • Air filters
  • COPD
  • Clinical trial
  • Environment
  • Particulate matter

ASJC Scopus subject areas

  • Critical Care and Intensive Care Medicine
  • Pulmonary and Respiratory Medicine


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