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Chronic Obstructive Pulmonary Disease
and Obstructive Sleep Apnoea
Walter T McNicholas
Department of Respiratory and Sleep Medicine, St Vincent’s University Hospital, School of Medicine, University College Dublin, Dublin, Ireland
T he overlap syndrome (OS) of chronic obstructive pulmonary disease (COPD) and obstructive sleep apnoea (OSA) is common but
often missed in clinical practice. Different clinical COPD phenotypes influence the likelihood of co-existing OSA with the predominant
emphysema phenotype being protective whereas the predominant chronic bronchitis phenotype promotes the development of OSA.
The management of OS differs from COPD alone, particularly the use of nocturnal positive airway pressure (PAP), and patients with OS not
treated with PAP have a worse prognosis, which underlines the importance of correct diagnosis.
Keywords COPD, sleep apnoea, overlap syndrome,
mechanisms, phenotypes, management
Disclosure: Walter T McNicholas has no conflicts of
interest to declare in relation to this article. This article
is a short opinion piece and has not been submitted to
external peer reviewers. No funding was received in the
publication of this article.
Authorship: All named authors meet the International
Committee of Medical Journal Editors (ICMJE) criteria
for authorship of this manuscript, take responsibility
for the integrity of the work as a whole, and have
given final approval for the version to be published.
Open Access: This article is published under the
Creative Commons Attribution Noncommercial License,
which permits any non-commercial use, distribution,
adaptation and reproduction provided the original
author(s) and source are given appropriate credit.
Received: 20 February 2017
Published Online: 14 April 2017
Citation: European Respiratory & Pulmonary Diseases,
2017;3(1):23–4 Corresponding Author: Walter T McNicholas,
Department of Respiratory and Sleep Medicine, St
Vincent’s University Hospital, Elm Park, Dublin 4, Ireland.
For two such highly prevalent disorders, the co-existence of chronic obstructive pulmonary disease
(COPD) and obstructive sleep apnoea (OSA) in the same patient gets remarkably little attention in
routine clinical practice. Recent estimates indicate that up to 50% of adult males in the general
population have sleep-disordered breathing based on an apnoea-hypopnoea frequency (AHI) over
five events per hour, although the prevalence of a clinically significant disorder based on associated
symptoms is considerably lower. 1,2 COPD is also highly prevalent, with population estimates of 10%
for COPD associated with significant airflow obstruction. 3 Thus, by chance alone, COPD and sleep-
disordered breathing can be predicted to occur in about 3–4% of the general adult population, with
COPD and a clinically significant OSA syndrome occurring in 1–2%. 4 In considering the relationships
between COPD and OSAS, several questions can be considered. For example, does the presence
of either COPD or OSA increase the likelihood of the other disorder in an individual patient?
Does the presence of both disorders together, termed ‘overlap syndrome’, increase the likelihood
of co-morbidities? And what are the implications of overlap syndrome for patient management
Regarding COPD predisposing to OSA, one has to consider the influence of different COPD
phenotypes. In particular, the emphysema phenotype that is typically associated with lung
hyperinflation and low body mass index (BMI) is likely to be protective against OSA, 5,6 whereas
the chronic bronchitis phenotype that is associated with chronic productive cough, higher BMI,
and predisposition to cor pulmonale is more likely to predispose towards OSA. 7 Recent evidence
indicates that lung hyperinflation is associated with reduced pharyngeal collapsibility, 5 and AHI
is negatively correlated with the degree of emphysema on computed tomography (CT) of the
thorax in COPD patients. 6 Peripheral oedema in patients with cor pulmonale predisposes to OSA
as a result of rostral fluid shift during the night associated with the supine position, contributing
to narrowing of the oropharynx by fluid build-up. 8 The evidence that OSA contributes to COPD is
less clear, although there is some epidemiological evidence that both COPD and asthma are more
prevalent in patients with OSA, but the mechanisms of this association have not been established. 9
Concerning co-morbidities, COPD and OSA are both recognised as independent risk factors for
cardiovascular co-morbidity, 10,11 and it appears reasonable to postulate that patients with overlap
syndrome will be at greater risk of co-morbidity. However, there have been remarkably few reports
in the literature regarding the risk of cardiovascular disease in patients with overlap syndrome.
Overlap patients demonstrate more pronounced hypoxaemia during sleep than patients with
either COPD or OSA alone and therefore they are more prone to develop pulmonary hypertension. 12
Both COPD and OSA alone are associated with evidence of systemic inflammation, 13,14 which
is postulated as an important mechanism in the development of cardiovascular and metabolic
disease. However, there have been very few studies that have assessed measures of systemic
inflammation or other basic mechanisms that may contribute to cardiometabolic disease in
patients with overlap syndrome.
TOU CH MED ICA L MEDIA