Sleep Disturbance in Smokers with Preserved Pulmonary Function and with Chronic Obstructive Pulmonary Disease

Abstract

Rationale: Sleep disturbance frequently affects patients with chronic obstructive pulmonary disease (COPD), and is associated with reduced quality of life and poorer outcomes. Data indicate that smokers with preserved pulmonary function have clinical symptoms similar to those meeting spirometric criteria for COPD, but little is known about the driving factors for sleep disturbance in this population of emerging interest.

Objectives: To compare the magnitude and correlates of sleep disturbance between smokers with preserved pulmonary function and those with airflow obstruction.

Methods: Using cross-sectional data from the COPD Outcomes-Based Network for Clinical Effectiveness and Research Translation multicenter registry, we identified participants clinically identified as having COPD with a smoking history of at least 20 pack-years and either preserved pulmonary function or airflow obstruction. We quantified sleep disturbance by T-score measured in the sleep disturbance domain of the Patient-Reported Outcomes Information System questionnaire, and defined a minimum important difference as a T-score difference of two points. We performed univariate and multivariable linear regression to evaluate correlates within each group.

Results: We identified 100 smokers with preserved pulmonary function and 476 with airflow obstruction. The sleep disturbance T-score was 4.1 points greater among individuals with preserved pulmonary function (95% confidence interval [CI], 2.0-6.3). In adjusted analyses, depression symptom T-score was associated with sleep disturbance in both groups (airflow obstruction: β, 0.61 points; 95% CI, 0.27-0.94; preserved pulmonary function: β, 0.25 points; 95% CI, 0.12-0.38). Of note, lower percent predicted FEV₁ was associated with greater sleep disturbance among those with preserved pulmonary function (β, -0.19 points; 95% CI, -0.31 to -0.07), whereas higher FEV₁ was associated with greater sleep disturbance among individuals with airflow obstruction (β, 0.06 points; 95% CI, 0.01-0.10).

Conclusions: Among smokers with clinically identified COPD, the severity of sleep disturbance is greater among those with preserved pulmonary function compared with those with airflow obstruction. Nonrespiratory symptoms, such as depression, were associated with sleep disturbance in both groups, whereas the relationship of sleep disturbance with FEV₁ differed.

Keywords: chronic obstructive pulmonary disease; sleep initiation and maintenance disorders; smoking.

Figure 1.

Symptoms reported among participants with preserved pulmonary function and with airflow obstruction. Shown is the proportion of participants in each group with respiratory and nonrespiratory symptoms of interest. For symptoms measured continuously by T-score, the cutoff is made at a score of 52 (general population mean plus the minimum important difference of 2). Error bars refer to 95% confidence intervals. Proportions compared by χ² test; *P < 0.05. Dist. = disturbance; PND = paroxysmal nocturnal dyspnea.