Effects of air purifiers on rhinitis quality of life and perception of sleep quality in people with asthma: Randomised controlled trial

be-tween Placebo and Intervention for any of the three questions on sleep quality. However, the group medians of total score/patient over 11 visits for each of the sleep questions (visualised using box plots) showed a significant improvement in sleep quality in the intervention group [getting to sleep better (Q1, p - value: < .0001)], not waking up at night as often (Q2, p - value: .021). Scores for the question on ‘lack of good night's sleep’ were similar for the two groups (Q3, p - value: .080). The age-adjusted repeated measures analysis with sleep scores confirmed these findings. The strengths of our study include the longest follow-up (18 months), minimal dropout rate and repeated measures design affording high statistical power to distinguish between the effects of placebo and active air purifiers. A limitation is that RQLQ and sleep quality were post hoc objectives and should be treated as a hypothesis-generating study. Further confirmatory studies are required. Against the backdrop of climate change, rhinitis is a worsening global health problem. Several studies have demonstrated the link between quality of sleep and health and disease. 7 In this context, our intervention may potentially serve as an adjunct therapy to tackling these conditions. Key findings were no difference between treatments in end- of-study analyses, but indications of improvements in both rhinitis-related QoL and patients' perception of sleep in the intervention group in repeated measures analysis. Park et al. demonstrated an improvement in rhinitis symptom scores with HEPA filtration. 8 A 2-week crossover study demonstrated the benefits of air purification on sleep in healthy individuals. 9 Demonstration of improvement in post hoc analyses of rhinitis QoL and sleep in a randomised control trial over 18 months warrants testing the use of air purifiers in improving QoL in individuals with rhinitis in an adequately powered randomised trial


Effects of air purifiers on rhinitis quality of life and perception of sleep quality in people with asthma: Randomised controlled trial
To the editor, Good indoor air quality (IAQ) is important for optimal respiratory health.Air purifiers with high-efficiency particulate air (HEPA) filters reduce particulate matter (PM) concentrations and improve IAQ, 1 but health impact is uncertain possibly because of the short duration of previous studies. 2We conducted a single-centre, doubleblinded, randomised, placebo-controlled trial to examine the effects of improved IAQ on adult asthma using a novel HEPA air purifier, the Dyson Pure Cool™, with numerous distinct characteristics compared to other purifiers. 3e trial was conducted on the Isle of Wight, United Kingdom, over 78 weeks (September 2019 to July 2021). 4,5Fifty patients, aged 18-75 years with physician-diagnosed mild to moderate persistent and uncontrolled asthma, were randomised at a 1:1 ratio identicallooking purifiers with either active (Intervention, N = 25) or dummy filters (Placebo, N = 25).The primary objective was to assess the impact on asthma. 4,5We also collected longitudinal data on rhinitis and sleep quality of life (QoL) using the Juniper Rhinitis Quality of Life Questionnaire (RQLQ) 6 as an exploratory post hoc analysis.
Air purifiers with dummy or active HEPA filters measured airborne particulate matter (PM 2.5 ) continuously, while only the active filter purifier reduced PM 2.5 . 3,5Longitudinal data on rhinitis QoL, collected at 11 time points (~6 weekly intervals) were analysed by fitting multivariable repeated measures models (linear regression). 5itial models were controlled for sex, age, asthma-and allergyrelated factors, smoking status, pets and air pollutants at home (dust, pollution from traffic near home, air quality parameters) and at work (patient-reported).Factors associated with RQLQ scores with p-values ≤.1 were identified via stepwise backward elimination and included in the final model.
Longitudinal data on the participants' perception of sleep quality were collected at 11 time points (~6 weeks' intervals) using a set of three questions within the RQLQ (scores 0-6, for best to worst sleep quality).All 50 participants responded with minimal missing data (Placebo: 0.4%; Intervention: 4%).Scores reported over 11 assessments were summed separately for each of the three questions for each patient.Medians of the total score/patient/question for Placebo and Intervention were compared visually using box plots TA B L E 1 Comparison of the rhinitis quality of life questionnaire (RQLQ) scores of placebo and intervention groups using multivariable linear regression analysis.Both study groups were well matched in patient characteristics and PM 2.5 concentrations at baseline. 5The annual mean PM 2.5 concentration during the year 2020 (4 months after the start of the trial when data for 12 months were available for all patients) was significantly lower for Intervention (5 μg/m 3 ) than for Placebo (8.15 μg/m 3 ) (p-value for the difference: .0003). 5 Baseline RQLQ scores were similar for the placebo and in-  1).

The change in sleep
QoL from baseline to the end of the trial, ignoring the intermediate scores, was not significantly different between Placebo and Intervention for any of the three questions on sleep quality.However, the group medians of total score/patient over 11 visits for each of the sleep questions (visualised using box plots) showed a significant improvement in sleep quality in the intervention group [getting to sleep better (Q1, p-value: <.0001)], not waking up at night as often (Q2, p-value: .021).Scores for the question on 'lack of good night's sleep' were similar for the two groups (Q3, p-value: .080).The age-adjusted repeated measures analysis with sleep scores confirmed these findings.The strengths of our study include the longest follow-up (18 months), minimal dropout rate and repeated measures design affording high statistical power to distinguish between the effects of placebo and active air purifiers.A limitation is that RQLQ and sleep quality were post hoc objectives and should be treated as a hypothesis-generating study.Further confirmatory studies are required.Against the backdrop of climate change, rhinitis is a worsening global health problem.Several studies have demonstrated the link between quality of sleep and health and disease.7In this context, our intervention may potentially serve as an adjunct therapy to tackling these conditions.Key findings were no difference between treatments in end-of-study analyses, but indications of improvements in both rhinitis-related QoL and patients' perception of sleep in the intervention group in repeated measures analysis.Park et al. demonstrated an improvement in rhinitis symptom scores with HEPA filtration. 8A 2-week crossover study demonstrated the benefits of air purification on sleep in healthy individuals. 9Demonstration of improvement in post hoc analyses of rhinitis QoL and sleep in a randomised control trial over 18 months warrants testing the use of air purifiers in improving QoL in individuals with rhinitis in an adequately powered randomised trial.K E Y WO R DS clinical trial, DYSON air purifier, quality of life, repeated measures, rhinitis, sleep

Number analysed Coefficient (95% CI) p-Value Placebo Intervention
RQLQ scores of the intervention group (Dyson purifiers with active HEPA filters) were compared to that of the placebo group (with dummy filters) using multivariable linear regression analyses (random intercept models for longitudinal data).The analyses included a total of 537 data points (out of a possible 550) collected from 25 participants from each of the groups who were followed up 11 times during the study.The risk factors are independently associated with RQLQ as identified in a stepwise backward elimination procedure starting from a fully adjusted model with 22 potential risk factors.Abbreviations: BMI, body mass index; CI, confidence intervals; Coefficient, regression coefficient; RQLQ, Juniper rhinitis quality of life questionnaire.a Negative coefficients (reduction in RQLQ) indicate better rhinitis quality of life in the intervention group.