Study Finds That Physical Hallmarks of COPD May Not Be Main Cause of Sleep Disturbances

Pulmonary function variables characteristic of chronic obstructive pulmonary disease (COPD) were found to have an impact on sleep quality but only by a slight amount, according to a recent study.

“The direct contribution of these pathophysiological hallmarks of COPD to objectively measured sleep quality seems to be less important than it is generally thought, highlighting the complex pathogenesis of sleep disorders in this population of patients,” wrote the investigators.

The retrospective cross-sectional study, published in the Jornal Brasileiro de Pneumologia, clarifies the role that pulmonary function factors have on sleep quality and architecture in patients with COPD. It also opens the door for researchers to investigate the impact that psychological conditions and other mechanisms commonly associated with COPD and sleep disturbances may have on sleep.

Disturbed sleep is a frequent complaint among patients with COPD and is ranked as the third most troublesome disturbance behind dyspnea and fatigue. Low sleep efficiency, disturbed sleep architecture, and problems falling and staying asleep can be observed using overnight polysomnography (PSG). However, mechanisms that cause sleep quality to become impaired are often contested.

Altered respiratory mechanics and abnormalities in gas exchange may elevate patients’ risk of developing nocturnal hypoventilation and hypoxemia. Previous research has suggested that airflow obstruction and lung hyperinflation are correlated with worsened sleep quality and that oxygen desaturation may impair sleep architecture. Other common COPD factors thought to influence sleep include obesity, cardiovascular and metabolic comorbidities, and polypharmacy.

The investigators analyzed data from 181 patients with COPD who were 40 years or older, referred to the Clinical Laboratories of Queen’s University Affiliated Teaching Hospitals in Kingston, Canada, and had results available for spirometry with postbronchodilator assessment, whole-body plethysmography, diffusing capacity of the lungs for carbon monoxide (DLCO), and overnight PSG between 2008 and 2016.

COPD severity varied among the included patients, of whom 73 (40.3%) had mild disease, 78 (43.1%) had moderate COPD, and 30 (16.6%) had severe or very severe COPD. The patients all presented with impaired ventilatory mechanics and DLCO at rest.

PSG levels showed that 64.1% of patients had obstructive sleep apnea (OSA) and a high proportion of patients had significant nocturnal desaturation, with a mean (SD) pulse oximetry nadir level of 82.2% (6.9%).

The results from the univariate linear regression analyses revealed that selected resting lung function measures were slightly correlated with sleep quality and architecture parameters.

After adjusting for confounding variables, the multivariate analyses demonstrated that pulmonary function parameters were independent predictors of sleep quality, sleep onset latency, and REM sleep. The ratio of amount of air exhaled in 1 second vs the amount exhaled in a full breath was a predictor for sleep efficiency. DLCO was an independent predictor of sleep onset latency and REM sleep.

“Although several weak relationships were observed in univariate regressions, few lung function variables remained in the multivariate models only predicting sleep efficiency, sleep onset latency, and [percentage] of REM sleep, and all final multivariate models demonstrated low coefficients of determination. This means that only a small proportion of the variance in the dependent variables could be predicted from the independent variables,” the investigators said.

The investigators listed the cross-sectional and retrospective design of the study as a limitation of the study. Additionally, they said that lack of assessment of anxiety and depression in their study population may have altered the results.

“It seems reasonable to consider these functional abnormalities in conjunction with other clinical signs of the disease (nocturnal wheezing, cough, and phlegm), COPD-related psychological distress, and polypharmacy in order to estimate the likelihood of poor sleep quality in individual patients,” the investigators noted.

Reference

Marques RD, Berton DC, Domnik NJ, et al. Sleep quality and architecture in COPD: the relationship with lung function abnormalities. J Bras Pneumol. Published online July 19, 2021. doi:10.36416/1806-3756/e20200612