CME Author: Vicki Brower
Study Authors: Matthew Shorofsky, Jean Bourbeau, et al.
Target Audience and Goal Statement:
Pulmonologists, allergists/immunologists, geriatricians, sleep disorder specialists, internists, family medicine specialists
The goal of the study was to evaluate the relationship between subjective sleep quality and risk of chronic obstructive pulmonary disease (COPD) exacerbations in a population-based sample.
- What is the relationship between COPD and sleep disorders with regard to exacerbations of COPD?
Study Synopsis and Perspective:
Poor sleep quality, assessed using a validated subjective sleep questionnaire, was associated with higher COPD exacerbation risk over 18 months of follow-up in a Canadian prospective cohort study.
- Poor sleep quality, assessed using a validated subjective sleep questionnaire, was associated with higher COPD exacerbation risk over 18 months of follow-up in a prospective cohort study.
- Understand that routine assessment of sleep quality may be a useful clinical predictor of exacerbation risk, and a tool to identify those who might benefit from closer follow-up and interventions.
Among 141 people with physician-diagnosed COPD, each 2-point increment in Pittsburgh Sleep Quality Index (PSQI) scores was associated with a 9% increased risk of symptom-based exacerbations (adjusted relative risk 1.09, 95% CI 1.01-1.18, P=0.02), and a 10% increase in risk for “event-based” exacerbations (symptoms plus medication or unscheduled use of medical services, adjusted RR 1.10, 95% CI 1.00-1.22, P=0.048), according to Marta Kaminska, MD, of McGill University Health Centre in Montreal, and colleagues.
Those with symptomatic exacerbations had higher median PSQI scores (median 6.0 vs 5.0, P=0.01) and were also more likely to have baseline PSQI scores greater than 5 (50.3% vs 37.3%, P=0.01), they reported in CHEST.
Sleep disorders are common in patients with COPD, with the frequent concurrence of COPD and obstructive sleep apnea (OSA) recognized as an overlap syndrome with an elevated risk for exacerbations and hospitalizations.
But the current findings from the Canadian Cohort Obstructive Lung Disease (CanCOLD) study are among the first to show elevated exacerbation risk associated with general sleep disturbance in patients with previously diagnosed and undiagnosed COPD, the authors noted.
“Poor sleep was associated with greater future risk of exacerbations, worsened symptoms, and more hospitalizations,” Kaminska told MedPage Today. “We ask patients with asthma about sleep symptoms all the time, because we know that poor sleep is a marker for poor asthma control. COPD hasn’t really been on many people’s radar, but we should probably be asking patients with COPD about sleep too.”
Kaminska and colleagues analyzed 480 CanCOLD participants with COPD (mean age 68, about 63% men) drawn from the full study sample of 6,592 people identified through random telephone calling. COPD was confirmed using spirometry in participants without a previously confirmed diagnosis. Participants included in the analysis had 18 months of follow-up. COPD had not been previously diagnosed in 339 of the participants.
Of the patients included in the analysis, 185 experienced one or more exacerbations during follow-up and 203 reported poor baseline sleep quality (PSQI >5).
Researchers noted that the strongest associations they found were for sleep disturbances and daytime dysfunction, and that the time to symptom-based exacerbation was shorter in people with poor sleep quality (adjusted HR 1.49, 95% CI 1.09-2.03).
Subgroup analysis showed that the association between sleep quality and COPD exacerbations was stronger in the undiagnosed COPD patients. After adjusting for confounders, exacerbations in this group were strongly related to a PSQI >5, higher global PSQI, and Factor 2 and 3 scores.
“These associations were generally not found in diagnosed COPD,” the researchers wrote. “This difference between diagnosed and undiagnosed participants may be related to high prevalence of poor sleep quality and [a] higher exacerbation rate in the diagnosed group.”
Study strengths included the use of the CanCOLD population-based cohort that contains individuals with all COPD severities.
The researchers concluded that “the relationship between exacerbations and sleep quality is probably bi-directional.”
They added that the observation that the Kaplan-Meier curves for exacerbation-free survival only began to diverge after the first 1 or 2 months “suggests that baseline poor sleep quality is not connected to an ongoing or impending exacerbation, though it may reflect more unstable disease.”
The authors noted that additional studies are needed to explore the mechanisms of interaction between sleep disturbances and COPD exacerbations, and to determine whether interventions to improve sleep quality can change COPD-related outcomes.
“Routine assessment of sleep quality may be a useful clinical predictor of exacerbation risk, and a tool to identify those who might benefit from closer follow-up and interventions,” they stated.
Study limitations included the fact that individuals with asthma or other obstructive lung diseases could not be definitively excluded, as methacholine challenges were not conducted. In addition, no objective sleep assessment, such as polysomnography was performed, and therefore the study results were based on subjective sleep quality alone.
“The sample size may have been insufficient to demonstrate certain associations, particularly in subgroup analyses,” the authors acknowledged. “Despite these limitations, we believe that our prospective follow-up findings suggest that poor sleep quality can be a marker of an exacerbating COPD.”
Source Reference: CHEST 2019; DOI: 10.1016/j.chest.2019.04.13
Study Highlights: Explanation of Findings
This study demonstrates that poor subjective sleep quality in patients with COPD was associated with increased risk of exacerbations during 18 months’ follow-up, in particular, in those with undiagnosed COPD. Higher baseline PSQI scores were associated with increased risk of COPD symptom- and event-based exacerbations during this time period.
Notably, individuals with poor sleep quality experienced a shorter time to symptom-based exacerbation, the authors reported.
The study is the first population-based longitudinal study evaluating risk of exacerbation in relation to subjective sleep disturbances, and assessing previously diagnosed and undiagnosed COPD, they stated.
Patients with COPD commonly experience sleep disorders, including insomnia, hypnotic medication use, and excessive daytime sleepiness, as well as changes in ventilation at night, cough, and wheeze, as measured by the PSQI. Sleep quality is an important predictor of health-related quality of life in COPD, and acute exacerbations are common in this disease, and can contribute to health deterioration and higher mortality. As a result, there has been a growing interest in sleep quality in COPD and its effect on disease-related exacerbations, according to the authors.
In this study, exacerbations were considered to be either symptom-based or event-based. The former required at least 1 of increased dyspnea, sputum volume or purulence, lasting at least 48 hours, whereas the latter was defined as a symptom-based exacerbation plus the use of antibiotics, corticosteroids, or accessing healthcare services.
Of note, the majority of COPD patients were undiagnosed by a doctor, 71%, and those who had been diagnosed were more likely to be prescribed inhaled treatment; this group had poorer quality sleep than those who were undiagnosed with COPD, and more likely to have at least one exacerbation in the follow-up period. The overall exacerbation rate was higher in patients who had been diagnosed.
Kaminska said multiple mechanisms could explain the relationship between poor sleep and respiratory issues.
“Poor sleep may be related to [undiagnosed OSA], which is a recognized risk factor for COPD exacerbations, and it may be a marker of more severe COPD,” she said.
Poor respiratory function related to COPD could also lead to sleep disturbance and poor sleep quality might trigger changes in COPD control, she added. The relationship is likely bi-directional: poor respiratory function could lead to sleep problems, and poor sleep quality could trigger change in COPD control, increasing daytime symptoms and having a negative effect on immune function. This in turn could increase susceptibility to infections, increase inflammation, and worsen COPD control and up exacerbation risk.
Kaminska also pointed out that there is growing interest in the link between OSA and COPD, with observational studies finding that treatment of OSA in COPD is associated with reduced mortality, exacerbations, and hospitalizations.
Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco