Total Sleep Time in the Taiwan Obstructive Lung Disease Cohort

Abstract

Patients with chronic obstructive pulmonary disease (COPD) have been reported to have poor sleep quality. However, total sleep time has not been evaluated in detail among patients with COPD. This retrospective, observational, multicenter research study was performed across six participating hospitals in Taiwan, with a total of 421 adult patients enrolled. Pulmonary function, the Modified British Medical Research Council Dyspnea Scale, the COPD Assessment Test and basic clinical data were assessed. The Pittsburgh Sleep Quality Index was also administered to patients, and the total sleep time was extracted for further analysis. The patients whose total sleep time was between 6 and 7 h had better pulmonary function, and the patients who slept less than 5 h had worse comorbidities. There was a significant higher total sleep time in Global Initiatives for Chronic Obstructive Lung Disease (GOLD) group B compared to GOLD group A. COPD patients who sleep between 5 and 6 h used fewer oral steroids and were less likely to use triple therapy (long-acting beta-agonist, long-acting muscarinic antagonist, inhaled cortical steroid). COPD patients sleeping from 5 to 7 h had better clinical features than those sleeping less than 5 h in terms of pulmonary function, comorbidities and medication usage.

Keywords: COPD; PSQI; comorbidity; pulmonary function; total sleep time.

Figure 1

The assessment of pulmonary function in 4 different total sleep time groups from spirometry. (a) The post bronchodilator predicted forced expiratory volume in 1 s (FEV₁(%)) was lower in patients who sleep less than 5 h than in patients who sleep between 6 and 7 h. (b) The trend of lower forced vital capacity (FVC (%)) appeared in patients who sleep less than 5 h, although no statistical significance was found. Note: 95% confidence interval, *: p < 0.05 vs. 6~7 h. Abbreviations: FEV₁ = forced expiratory volume in one second, FVC = forced vital capacity.

Figure 2

The influence of different GOLD groups on total sleep time in COPD patients. (a) There was a significant increase in total sleep time in GOLD group B compared to GOLD group A. (b) There was no significant difference in total sleep time among low-risk patients (group A and B) compared to high-risk patients (group C and D). (c) There was a significant higher total sleep time in COPD patients with more symptoms (group B and D) compared to fewer symptoms (group A and C). Note: 95% confidence interval, *: p < 0.05 vs. Group A; #: p < 0.05 vs. Group A + C. Abbreviations: GOLD = Global Initiative for Chronic Obstructive Lung Disease.

Figure 3

A directed acyclic graph (DAG) was drawn to identify the minimum set of confounders. The minimal sufficient adjustment sets for estimating the direct effect of FEV₁ on total sleep time are age, CAT, exacerbation, gender, heart failure, oral steroids and xanthine. Abbreviations: BMI = body mass index; CAT = COPD Assessment Test; DM = diabetes mellitus; FEV₁ = forced expiratory volume in one second. Legends: green square = ancestor of exposure; blue square = ancestor of outcome; pink square = ancestor of exposure and outcome; transparent square = other variables; green arrow = causal path; pink arrow = biasing path.