Affiliations: Seattle, WA
Dr. Loube is Director, Sleep Disorders Center, Virginia Mason Medical Center.
Correspondence to: Daniel Loube, MD, FCCP, Virginia Mason Medical Center, Sleep Disorders Center (H-10), 925 Seneca St, Seattle, WA 98111; e-mail: email@example.com
Recently, two well-designed studies by researchers from the
University of Wisconsin1and the Sleep Heart Health
Study Group2 documented that untreated obstructive sleep
apnea (OSA) increases the risk for hypertension in American adults. In
both studies, the risk for hypertension increased in a dose-response
association with the frequency of obstructive respiratory events during
the night, independently of confounding factors such as age, gender,
and weight. It is expected that these and other studies evaluating
large patient cohorts will determine whether this increased risk for
hypertension results in added morbidity and mortality from ischemic
heart disease and other cardiovascular diseases. It may well be that
the increased risk of cardiovascular disease sequelae from OSA will
warrant widespread efforts at early detection and treatment, much as is
the current clinical practice for hyperlipidemia.
Sleep apnea is typically characterized as a disease of obese,
middle-aged men.3–4 This stereotype is a result of older
studies completed in the United States, Europe, and Australia that
found that 60 to 90% of all OSA patients are obese,5as
defined by a body mass index (BMI) of ≥ 28
kg/m2. A landmark study by Young et
al6 determined that 2 to 4% of Wisconsin factory workers
had OSA, and that the risk for OSA increased in close association with
measures of truncal obesity, such as neck size. The study by Ip et al
in this issue of CHEST (see page 62) indicates that OSA may
occur with a similar prevalence in a cohort of nonobese subjects, as
the mean BMI for this study cohort was only 23.9
kg/m2. Of great importance is the fact that the
study cohort was 784 Chinese office workers in Hong Kong.
There are a paucity of data characterizing the epidemiology of OSA in
populations other than middle-aged or older white men, and few studies
have focused on young adults, women, or patients of African or Asian
descent. Recent investigations on the epidemiology of ischemic heart
disease indicate that the clinical recognition and management of this
disease varies markedly in cohorts of women7or of
nonwhite patients, compared with that of white men.8 The
scenario may be much the same for the epidemiology of OSA.
The study by Ip et al suggests, in a preliminary fashion, that the
demographics and even possibly the pathogenesis of OSA may be different
for Asians in comparison with whites. Along these lines, a recent study
by Li et al9 documented that Asian patients with OSA were
less obese but had more severe symptoms than whites presenting over the
same 1-year study interval. The authors attempted to attribute these
differences to various facial characteristics derived by radiographic
measurements that vary between Asians and whites. However,
demonstrating an association does not indicate a causal relationship.
A crucial conclusion from these studies is that predictive equations
for the presence of OSA developed from populations of obese, white men
and based on weight or facial measurements are unlikely to be accurate
in Asian men or, indeed, in many other groups. Such predictive
equations are often promoted as less-costly recognition strategies for
OSA than conventional 12-channel polysomnography. Their use is almost
certain to gain broader application if earlier and widespread diagnosis
of OSA becomes a public-health issue similar in significance to
hyperlipidemia as a risk factor for increased cardiovascular morbidity
The study by Ip et al is an important first step in illustrating that
fundamental differences may occur in various ethnic populations of OSA
patients. Recently, O’Connor et al10 showed that
important differences also exist between populations of women and men
with OSA. It is obvious that more studies are necessary to facilitate
and allow for the accurate diagnosis and appropriate treatment of OSA
in those other than middle-aged, white men.
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