The Epidemiology of Adult Obstructive Sleep Apnea
Naresh M. Punjabi1
1Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, Maryland
Obstructive sleep apnea is a chronic condition characterized by
nocturnal sleep quality and ensuing daytime fatigue and sleepiness
are widely acknowledged. Increasingly, obstructive sleep apnea is
also being recognized as an independent risk factor for several
clinical consequences, including systemic hypertension, cardiovas-
cular disease, stroke, and abnormal glucose metabolism. Estimates
of disease prevalence are in the range of 3% to 7%, with certain
subgroups of the population bearing higher risk. Factors that in-
crease vulnerability for the disorder include age, male sex, obesity,
family history, menopause, craniofacial abnormalities, and certain
health behaviors suchas cigarette smoking andalcoholuse. Despite
the numerous advancements in our understanding of the patho-
affected remain undiagnosed. Simple queries of the patient or bed-
partner for the symptoms and signs of the disorder, namely, loud
tify those in need of further diagnostic evaluation. The primary ob-
jective of this article is to review some of the epidemiologic aspects
of obstructive sleep apnea in adults.
Keywords: obstructive sleep apnea; sleep-disordered breathing;
Obstructive sleep apnea is being increasingly recognized as an
important cause of medical morbidity and mortality. It is a rela-
tively common sleep disorder that is characterized by recurrent
episodes of partial or complete collapse of the upper airway
The health consequences of obstructive sleep apnea are numer-
ous. If left untreated, it leads to excessive daytime sleepiness,
cognitive dysfunction, impaired work performance, and decre-
ments in health-related quality of life. Observational and exper-
imental evidence also suggests that obstructive sleep apnea may
contribute to the development of systemic hypertension (1), car-
diovascular disease (2), and abnormalities in glucose metabolism
(3). Obstructive sleep apnea is insidious and patients are often
unaware of the associated symptoms. Cardinal manifestations
include loud snoring, witnessed breathing pauses during sleep,
nition and appropriate therapycan ameliorate theneurobehavioral
consequences and may also have favorable effects on cardiovas-
cular health (4).
Clinical descriptions of obstructive sleep apnea can be found
in numerous reports published in the medical literature over the
last century (5). However, it was not until the 1980s that the clin-
ical ramifications of disorder became more widely appreciated
by the medical community. Although public awareness of obstruc-
tive sleep apnea has steadily increased since then, a majority of
those affected still remain undiagnosed. Thus, primary care phy-
sicians and specialists across various medical disciplines should
be sufficiently knowledgeable to identify those affected with this
disease. In this article various epidemiologic aspects of adult
obstructive sleep apnea are considered, with a particular em-
phasis on issues related to the population prevalence, natural
history, and factors that increase the predisposition for the
disorder. Before embarking on these issues, the methods used
to identify and diagnose the condition are briefly reviewed.
DISEASE DEFINITION AND DIAGNOSIS
The overnight polysomnogram is the standard diagnostic test for
obstructive sleep apnea. It involves simultaneous recordings of
multiple physiologic signals during sleep, including the electro-
encephalogram, electrooculogram, electromyogram, oronasal air-
flow, and oxyhemoglobin saturation. Collectively, these recordings
allow identification and classification of sleep-related apneas and
hypopneas. An apnea is defined as the complete cessation of air-
flow for at least 10 seconds. Apneas are further classified as ob-
structive, central, or mixed based on whether effort to breathe is
present during the event. A hypopnea is defined as a reduction in
airflow that is followed by an arousal from sleep or a decrease in
pnea require a 25% or 50% reduction in oronasal airflow asso-
ciated either with a reduction in oxyhemoglobin saturation or an
arousal from sleep (6). Sleep apnea severity is typically assessed
with the apnea–hypopnea index (AHI), which is the number of
apneas and hypopneas per hour of sleep. Several additional
measures of disease severity that characterize the degree of noc-
turnal hypoxemia (e.g., average oxyhemoglobin desaturation) and
extentof sleep fragmentation (i.e., arousalfrequency) are also used
in the clinical and research arenas.
Although considered as a ‘‘gold-standard,’’ the polysomno-
gram is not without limitations. It requires an overnight stay in
and interpret complex physiologic data. The process is time con-
suming, labor intensive, and can be costly. Moreover, despite re-
analysis, and interpretation of the polysomnogram across differ-
ent laboratories have made it difficult to compare various studies
ability, and the ‘‘first-night’’ effect explain some of the variability
in results across different studies. While some of aforementioned
example, the oxyhemoglobin desaturation threshold (e.g., 3% or
4%) used for defininghypopneas can lead tovarying estimates of
disease severity. Awareness of such factors is vital to better un-
derstand how distinct studies with relatively comparable designs
produce widely discrepant estimates of prevalence or measures
of association. Methodologic issues notwithstanding, substantial
advancements have been made in our knowledge of the health
natural history, and risk factors of adult obstructive sleep apnea.
Supported by National Institutes of Health Grants HL-075078, HL-086862, and
Correspondence and requests for reprints should be addressed to Naresh M.
Punjabi, M.D., Ph.D., Associate Professor of Medicine and Epidemiology, Division
of Pulmonary and Critical Care Medicine, Johns Hopkins University, 5501
Hopkins Bayview Circle, Baltimore, MD 21224. E-mail: email@example.com
Proc Am Thorac Soc
Internet address: www.atsjournals.org
Vol 5. pp 136–143, 2008
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