Abstract
Background“Overlap syndrome” refers to obstructive sleep apnea (OSA) combined with chronic obstructive pulmonary disease (COPD), and has poorer outcomes than either condition alone. We aimed to evaluate the prevalence and possible predictors of overlap syndrome and its association with clinical outcomes in patients with COPD.MethodsWe assessed the modified Medical Research Council dyspnea scale (mMRC), Epworth sleepiness scale (ESS), COPD assessment test (CAT), Hospital Anxiety and Depression Scale (HADS), Charlson Comorbidity Index (CCI), and STOP-Bang questionnaire (SBQ) and performed spirometry and full overnight polysomnography in all patients. An apnea–hypopnea index (AHI) ≥ 5 events per hour was considered to indicate OSA. Risk factors for OSA in COPD patients were identified by univariate and multivariate logistic regression analyses.ResultsA total of 556 patients (66%) had an AHI ≥ 5 events per hour. There were no significant differences in age, sex ratio, mMRC score, smoking index, number of acute exacerbations and hospitalizations in the last year, and prevalence of cor pulmonale between the two groups (all p > 0.05). Body mass index (BMI), neck circumference, CAT score, CCI, ESS, HADS, and SBQ scores, forced expiratory volume (FEV)1, FEV1% pred, FEV1/forced vital capacity ratio, and prevalence of hypertension, coronary heart disease, and diabetes were all significantly higher and the prevalence of severe COPD was significantly lower in the COPD-OSA group compared with the COPD group (p < 0.05). BMI, neck circumference, ESS, CAT, CCI, HADS, hypertension, and diabetes were independent risk factors for OSA in COPD patients (p < 0.05). SBQ could be used for OSA screening in patients with COPD. Patients with severe COPD had a lower risk of OSA compared with patients with mild or moderate COPD (β = − 0.459, odds ratio = 0.632, 95% confidence interval 0.401–0.997, p = 0.048).ConclusionPatients with overlap syndrome had a poorer quality of life, more daytime sleepiness, and a higher prevalence of hypertension and diabetes than patients with COPD alone. BMI, neck circumference, ESS, CAT, CCI, HADS, hypertension, and diabetes were independent risk factors for OSA in patients with COPD. The risk of OSA was lower in patients with severe, compared with mild or moderate COPD.
Highlights
Chronic obstructive pulmonary disease (COPD) is a common, preventable and treatable disease characterized by chronic airflow limitation, which is not fully reversible [1]
There were no significant differences in age, sex, smoking index, number of acute exacerbations in the year before admission, hospital frequency, modified Medical Research Council dyspnea scale (mMRC) score, and cor pulmonale between the COPD group and COPD-Obstructive sleep apnea (OSA) group
body mass index (BMI), neck circumference, FEV1, FEV1 (%predicted), FEV1/ forced vital capacity (FVC), apnea–hypopnea index (AHI), COPD assessment test (CAT), Epworth sleepiness scale (ESS), STOP-Bang questionnaire (SBQ), Hospital Anxiety and Depression Scale (HADS)-A, and HADS-D scores, and the incidences of hypertension, coronary heart disease, and diabetes were all significantly higher and the proportion of severe COPD [(FEV1 (%predicted) < 50%] was significantly lower in the COPD-OSA group compared with the COPD group
Summary
Chronic obstructive pulmonary disease (COPD) is a common, preventable and treatable disease characterized by chronic airflow limitation, which is not fully reversible [1]. Overlap syndrome has more serious adverse effects on the quality of life in patients with COPD [7, 8] Because of their similar pathophysiological effects, especially in terms of hypoxia and systemic inflammation, the simultaneous occurrence of COPD and OSA has more severe nocturnal hypoxemic and hypercarbia effects than either COPD or OSA alone, and is more likely to be complicated with cardiovascular diseases [7, 9]. Overlap of these two conditions can reduce daytime oxygen saturation and quality of life-related scores, and increase the frequencies of acute exacerbation, comorbidity, economic burden and mortality due to COPD [7, 10, 11]. We conducted a crosssectional community-based study in China to clarify the prevalence, clinical characteristics, risk factors of COPD with OSA, and the relationship between airflow limitation in COPD and severity of OSA
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