Poor sleep quality, assessed using a validated sleep questionnaire, was associated with higher COPD exacerbation risk over 18 months of follow-up in a Canadian prospective cohort study.
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, Montreal, and colleagues.
Those with symptomatic exacerbations had higher median PSQI scores (median 6.0, IQR 3.0-8.0, vs 5.0, IQR 2.0-7.0, P=0.01) and were also more likely to have baseline PSQI scores greater than 5 (50.3% vs 37.3%, P=0.01), the researchers 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 new 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.
“Poor sleep was associated with greater future risk of exacerbations, worsened symptoms, and more hospitalizations,” Kaminska told 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,” she said. “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).
The strongest associations were seen for sleep disturbances and daytime dysfunction and 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 greater than 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 higher exacerbation rate in the diagnosed group.”
Kaminska said multiple mechanisms could explain the relationship between poor sleep and respiratory issues.
“Poor sleep may be related to [undiagnosed obstructive sleep apnea], 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 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 sample size may have been insufficient to demonstrate certain associations, particularly in subgroup analyses,” they wrote. “Despite these limitations, we believe that our prospective follow-up findings suggest that poor sleep quality can be a marker of an exacerbating COPD.”
The CanCOLD study is currently funded by AstraZeneca Canada, Boehringer Ingelheim Canada, GlaxoSmithKline Canada, and Novartis.
Kaminska reported grants from AstraZeneca Canada, Boehringer Ingelheim Canada, GlaxoSmithKline, Almirall, Pfizer Canada, and others.
One co-author reported no relevant relationships with industry.