in an 18-month prospective study of 480 patients.
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“Poor sleep quality in COPD has previously been associated with reduced health-related quality of life and reduced physical activity during the day,” wrote Matthew Shorofsky, MD, of McGill University, Montreal, and associates. Their report is in CHEST. “However, to our knowledge, this is the first population-based longitudinal study evaluating exacerbation risk in relation to subjective sleep disturbances and assessing previously diagnosed and undiagnosed COPD.”
The study included participants enrolled in the Canadian Respiratory Research Network and the Canadian Cohort Obstructive Lung Disease (CanCOLD) study who had COPD, available baseline PSQI scores, and 18 months of follow-up data. The PSQI includes 19 questions on sleep quality, latency, duration, efficiency, disturbances, use of sleep medications, and daytime dysfunction. Total score ranges between 0 and 21, and a score above 5 is considered poor sleep. Online patient surveys and quarterly phone interviews were used to track symptom-based exacerbations (at least 48 hours of increased dyspnea, sputum volume, or sputum purulence) and event-based exacerbations (a symptom-based exacerbation plus the use antibiotics or corticosteroids or health services).
At baseline, 203 patients met the PSQI threshold for poor sleep quality. During follow-up, 185 patients had at least one COPD exacerbation. Poor sleep at baseline was significantly more prevalent among patients with symptoms-based COPD exacerbations (50.3%) than among patients without symptoms-based exacerbations (37.3%; P = .01). Poor baseline sleep quality remained a significant risk factor for symptom-based exacerbations of COPD even after the researchers accounted for the effect of age, gender, body mass index, smoking, depression, angina, baseline inhaled respiratory medications, forced expiratory volume in 1 second %predicted, and modified Medical Research Council (mMRC) dyspnea scale (adjusted risk ratio, 1.09; 95% confidence interval, 1.01-1.18; P =.02).
Patients with at least one symptomatic exacerbation of COPD were significantly more likely to meet the threshold for poor sleep quality on the Pittsburgh Sleep Quality Index and have significantly higher median PSQI scores compared with patients without exacerbations (6.0 [interquartile range, 3.0 to 8.0] vs. 5.0 [2.0 to 7.0]; P = .01). Poor baseline sleep quality also was associated with event-based exacerbations and with a shorter time to symptoms-based exacerbations. Sleep disturbances, such as rising to void or experiencing respiratory issues or pain during sleep, correlated most strongly with symptoms-based exacerbations.
Several factors could explain the link between poor sleep quality and COPD exacerbations, the investigators wrote. Patients with inadequately controlled COPD have more frequent and unstable respiratory symptoms, which could disrupt sleep either directly or indirectly (secondary to medication use or anxiety, for example). Conversely, sleep disruption can impede immune function and increase systemic inflammation, which might worsen COPD control and increase exacerbation risk. Poor sleep can impair memory and cognition, “potentially fostering medication nonadherence and symptom flare-up, especially in the older COPD population.” Although the link is poorly understood, patients with COPD often have comorbid obstructive sleep apnea (OSA), which is associated with COPD exacerbations, the researchers wrote. Treating OSA is associated with improved COPD morbidity and fewer exacerbations and hospitalizations.
The researchers acknowledged limitations to their study design. “Individuals with asthma or other obstructive lung diseases could not be definitively excluded; methacholine challenges were not performed. However, analyses excluding self-reported asthma were consistent with our main results. Second, because definitions of COPD exacerbation vary among studies, comparison may be limited, but CanCOLD used a standard definition, as recommended by GOLD.”
The CanCOLD study has received funding from the Canadian Respiratory Research Network, Astra Zeneca Canada, Boehringer Ingelheim Canada, GlaxoSmithKline Canada, Novartis, Merck Nycomed, Pfizer Canada, and Theratechnologies. Dr. Shorofsky had no disclosures. Several coinvestigators reported ties to GlaxoSmithKline, Novartis, Boehringer Ingelheim, Merck, Almirall, and Theratechnologies.
SOURCE: Shorofsky M et al. CHEST. 2019 May 28. doi: 10.1016/j.chest.2019.04.132.