Chronic obstructive pulmonary disease (COPD) increases susceptibility to sleep disturbances, which may, in turn, lead to an increase in respiratory symptoms, according to a study published in CHEST.

Researchers sought to examine the relationship between subjective sleep quality and COPD exacerbations in adults with physician-diagnosed and undiagnosed COPD. Participants with COPD who had completed 18 months’ follow-up in the Canadian Cohort Obstructive Lung Disease (CanCOLD; Identifier: NCT00920348) study were included. Self-reported sleep quality was measured using the Pittsburgh Sleep Quality Index (PSQI), which consists of 19 questions, grouped into 7 components and weighted on a scale from 0 to 3, with a score of >5 indicating poor sleep. A validated 3-factor analysis was also used where factor 1 measured sleep efficiency (sleep duration plus efficiency components, scored 0-6), factor 2 measured sleep quality (quality, latency, and medication use, scored 0-9), and factor 3 measured sleep disturbances (bathroom use, breathing issues, pain, etc.) and sleep-related daytime dysfunction (sleepiness, enthusiasm, etc., scored 0-6).

An exacerbation within the 18-month follow-up was the primary outcome variable. A symptom-based exacerbation required ≥1 of the following: increased dyspnea, sputum volume, or sputum purulence lasting ≥48 hours. An event-based exacerbation was defined as symptom-based exacerbation plus the use of antibiotics or corticosteroids or accessing healthcare services.

A total of 480 participants with COPD were studied, including 185 adults with ≥1 exacerbation during the follow-up period and 203 with poor baseline sleep quality (PSQI >5). Adults with symptom-based exacerbations had higher median baseline PSQI scores than those without (6.0; interquartile range, 3.0-8.0 vs 5.0; interquartile range, 2.0-7.0; P =.01), and were more likely to have baseline PSQI >5 (50.3% vs 37.3%; P =.01). Higher PSQI scores were associated with increased symptom-based exacerbation risks (adjusted risk ratio, 1.09; 95% CI, 1.01-1.18; P =.02) and event-based exacerbation risks (adjusted risk ratio, 1.10; 95% CI, 1.00-1.21; P =.048). The association occurred mainly in those with undiagnosed COPD. Strongest associations were with factor 3 (sleep disturbances). Time to symptom-based exacerbation was shorter in participants with poor sleep quality (adjusted hazard ratio, 1.49; 95% CI, 1.09-2.03).

Study limitations included adults with asthma and other obstructive lung diseases  were not excluded because methacholine challenges were not performed. Additionally, the definition of COPD has varied across studies. However, CanCOLD used the Global Obstructive Lung Disease (GOLD) recommended definition of COPD. Furthermore, self-reported exacerbations may also have been influenced by recall bias which has been remedied to some extent by the frequent telephone assessments, there were no objective assessments of sleep quality performed, individuals prone to COPD exacerbations may have experienced episodes of exacerbation prior to baseline thus excluding them from the study sample, and the sample size may have been insufficient to demonstrate the intended results.

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The researchers concluded that poor subjective sleep quality in individuals with COPD was associated with increased risk for exacerbations during 18 months’ follow-up, particularly in those with undiagnosed COPD. Thus, routine assessment of sleep quality might be a good predictor of exacerbation risk, helping in identifying those who may need close follow-up and more interventions. The researchers recommended that further studies be conducted to explore whether interventions to improve sleep quality can modify COPD-related outcomes.

Disclosures: The CanCOLD study is funded by the Canadian Respiratory Research Network (CRRN) and industry partners Astra Zeneca Canada Ltd, Boehringer Ingelheim Canada Ltd, GlaxoSmithKline Canada Ltd, and Novartis. Please see the  reference for a complete list of authors’ disclosures.


Shorofsky M, Bourbeau J, Kimoff J, et al; for the Canadian Respiratory Research Network and the CanCOLD Collaborative Research Group. Impaired sleep quality in COPD is associated with exacerbations: the CanCOLD cohort study [published online May 28, 2019]. CHEST. doi:10.1016/j.chest.2019.04.132