Portable air cleaners may improve respiratory outcomes in former smokers with COPD

Portable air cleaners improved respiratory outcomes among former smokers with COPD, with the greatest benefit found in those with greater adherence and those who spent more time indoors, according to results of the CLEAN AIR STUDY.

“Although outdoor air pollution has known adverse respiratory effects, the indoor environment is of particular concern, as most individuals with COPD spend the majority of their time indoors and indoor air particulate matter concentrations in homes of former smokers with COPD have been associated with worse respiratory symptoms, worse quality of life and increased respiratory exacerbations,” Nadia N. Hansel, MD, MPH, professor of medicine at Johns Hopkins University School of Medicine and from the department of environmental health and engineering at Johns Hopkins Bloomberg School of Public Health, and colleagues wrote.

The randomized controlled CLEAN AIR STUDY included 116 former smokers with moderate to severe COPD (mean age, 65.7 years; 51.7% women; 84.5% completed the study). All participants were randomly assigned to use an active portable high-efficiency particulate air (HEPA) cleaner (n = 58; Austin Air Cleaners) or a sham device that had internal HEPA and carbon filters removed (n = 58). Participants were asked to place the air cleaner in their bedroom and other room they reported spending the most time. Follow-up was 6 months. The intention-to-treat analysis included all participants, and the per-protocol analysis included participants with at least 80% adherence.

“Portable air cleaner intervention strategies are practical and easily implemented by individuals at the household level, and improve respiratory symptoms in other chronic respiratory diseases, including in children with asthma; however, such intervention studies have not been conducted in COPD and it is unknown whether use of portable air cleaners in homes of individuals with COPD can reduce indoor pollutants and improve COPD outcomes,” the researchers wrote.

The primary outcome was change in Saint George’s Respiratory Questionnaire (SGRQ) at 6 months.

The researchers reported no significant difference in total SGRQ score in either group, but the active air cleaner group had a greater reduction in SGRQ symptom subscale (beta = –7.7; 95% CI, –15 to –0.37) and respiratory symptoms (beta = –0.8; 95% CI, –1.5 to –0.1) compared with the sham air cleaner group.

At 6 months, there was no significant difference in the primary outcome between the two groups (SGRQ, –1.55; 95% CI, –5.75 to 2.65; P = .46) in the intention-to-treat analysis.

In addition, compared with the sham air cleaner group, the active group had lower rates of moderate COPD exacerbations (incidence rate ratio [IRR] = 0.32; 95% CI, 0.12-0.91) and rescue medication use (IRR = 0.54; 95% CI, 0.33-0.86).

In the per-protocol analysis, the researchers reported a significant difference in the 6-month change in SGRQ in the active air cleaner group compared with the sham group (beta = –4.76; 95% CI, –9.2 to –0.34). There were also significant differences in risk for moderate COPD exacerbations (beta = –0.51; 95% CI, –3.03 to –2), Breathlessness, Cough and Sputum Scale (beta = –0.81; 95% CI, –1.53 to –0.09) and 6-minute walk distance (beta = 54.5 m; 95% CI, –16.8 to 125.9).

Participants in the active air cleaner group who spent more time indoors were most likely to experience a treatment benefit from the HEPA air cleaners, with a greater improvement in SGRQ (–6.8; 95% CI, –12.55 to –1.06; P = .021), risk for COPD exacerbations (–3.92; 95% CI, –7.22 to –0.49; P = .023) and Breathlessness, Cough and Sputum Scale (–1.86; 95% CI, –2.82 to –0.9; P < .001) compared with the sham group.

“Though the study did not reach statistical significance for the primary outcome in intention-to-treat analysis, portable HEPA air cleaner use improved several respiratory outcomes, particularly among those with greater than 80% compliance with the air cleaner, and those that spent a larger portion of their time in their home,” the researchers wrote. “Interventions that improve air quality represent a potentially novel approach to reducing respiratory morbidity in patients with COPD and persistent respiratory symptoms and exacerbation risk despite smoking cessation. Further, given that environmental exposures contribute to a large proportion of COPD burden worldwide, the study may have broad implications.”