Fong WCG, Kadalayil L, Lowther S, Grevatt S, Potter S, Tidbury T, Bennett K, Larsson M, Nicolas F, Kurukulaaratchy R, Arshad SH. Ann Allergy Asthma Immunol. 2022 Oct 23:S1081-1206(22)01850-6. doi: 10.1016/j.anai.2022.10.010. Epub ahead of print.
Background: Air pollution is associated with poor asthma outcomes. High-efficiency particulate air (HEPA) air purifiers may reduce air pollution and thus improve asthma outcomes. However, the efficacy of such devices for this purpose remains inconclusive.
Objective: To investigate the effects of reducing the levels of pollutants on asthma outcomes in adults, using a novel DYSON HEPA air purifier.
Methods: In a single-centre, double-blinded, randomized controlled trial, participants (N=50) were randomized at a 1:1 ratio to active filters (Intervention) or to dummy filters (Placebo) for a total of 78 weeks. The primary outcomes were the changes in Asthma Control Questionnaire 6 (ACQ6) and Asthma-specific Quality of Life Questionnaire (AQLQ) scores, from baseline. The secondary outcomes were changes in indoor air pollution and lung function measurements. The Covid-19 pandemic limited spirometry measurements to two timepoints and assessment of Fractional Exhaled Nitric Oxide and Bronchial Hyper-responsiveness to baseline only.
Results: Air pollutant levels were significantly lower in the Intervention group compared to the Placebo group (p-value=0.0003). Both groups had a significant improvement in their ACQ6 and AQLQ. However, there were no significant between-group differences in ACQ6, AQLQ or spirometry, compared to baseline in multivariable repeated measures models.
Conclusion: The Dyson air purifier significantly improved air quality. However, there were no significant improvements in asthma control, quality of life or measures of lung function in the intervention group compared to the control group despite improvements in indoor air quality. Larger, extended studies are required to confirm or refute these findings, especially given that the Covid-19 pandemic prevented the procurement of detailed objective data.