Unrecognised obstructive sleep apnoea often co-exists with asthma and CPAP may improve some aspects of asthma patients’ quality of life, a pioneering study has shown.

In what has been described as the first randomised controlled trial of OSA treatment in patients with asthma, CPAP therapy for three months did not enhance asthma control but it did improve daytime sleepiness, quality of life and patient vitality.

Published in Respirology, the results of the trial conducted in Hong Kong were derived from an RCT involving 37 of 145 asthma patients (34%) found to have moderate to severe OSA as defined by an apnoea–hypopnea index (AHI) of 10 or more events per hour.

Patients also had severe asthma, with almost all taking high dose ICS/LABA, 80% taking montelukast and 34% also taking a long-acting muscarinic agonist (LAMA).

While CPAP adherence was good, with an average of more than five hours per night, there was no difference between CPAP treatment and control group (conservative treatment) in improvements in asthma control test scores over three months, with both groups showing similar levels of significant improvement (mean change 3.2 vs 2.4).

However, CPAP was associated with a greater improvement in had a greater improvement in Asthma Quality of Life Questionnaire (AQLQ) score (mean change 0.6 vs 0.02) and the vitality domain in the SF-36 questionnaire (14.7 vs 0.3)

Patients treated with CPAP also had had a greater improvement in Epworth Sleepiness Scale (−3.0 vs 0.5) than patients in the control group.

The study authors said their preliminary findings confirmed the high prevalence of co-existing asthma and OSA, which in observational studies had been around 50% of patients with asthma.

Alteration in pharyngeal airway patency, systemic inflammation, asthma medications or sleep fragmentation due to asthma may play a role in the development of OSA although the underlying mechanistic links remain to be tested,” they noted.

Commenting on the findings, Australian sleep physician Dr Garun Hamilton of the Epworth Sleep Centre, Melbourne, said clinicians should not be too pessimistic about the negative primary outcome because important practical lessons could be gained from from the secondary end points.

“With CPAP treatment clinically meaningful benefits were seen not only with respect to subjective sleepiness, but also with asthma-related quality of life and vitality. These are all relevant patient outcomes and highlight the widespread symptomatic benefits that are possible with CPAP treatment,” wrote Dr Hamilton in an accompanying commentary.

“It is therefore warranted to consider the possibility of OSA in all patients with difficult-to-control asthma, particularly those with habitual snoring, and to have a low threshold for offering polysomnography in those with symptoms that could be due to OSA,” he suggested.