Robert Wolk, Abu S.M. Shamsuzzaman and Virend K. Somers
Obesity, Sleep Apnea, and Hypertension
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Obesity, Sleep Apnea, and Hypertension
Robert Wolk, Abu S.M. Shamsuzzaman, Virend K. Somers
Abstract—Obesity has a high and rising prevalence and represents a major public health problem. Obstructive sleep apnea
(OSA) is also common, affecting an estimated 15 million Americans, with a prevalence that is probably also rising as
a consequence of increasing obesity. Epidemiologic data support a link between obesity and hypertension as well as
between OSA and hypertension. For example, untreated OSA predisposes to an increased risk of new hypertension, and
treatment of OSA lowers blood pressure, even during the daytime. Possible mechanisms whereby OSA may contribute
to hypertension in obese individuals include sympathetic activation, hyperleptinemia, insulin resistance, elevated
angiotensin II and aldosterone levels, oxidative and inflammatory stress, endothelial dysfunction, impaired baroreflex
function, and perhaps by effects on renal function. The coexistence of OSA and obesity may have more widespread
implications for cardiovascular control and dysfunction in obese individuals and may contribute to some of the
clustering of abnormalities broadly defined as the metabolic syndrome. From the clinical and therapeutic perspectives,
the presence of resistant hypertension and the absence of a nocturnal decrease in blood pressure in obese individuals
should prompt the clinician to consider the diagnosis of OSA, especially if clinical symptoms suggestive of OSA (such
as poor sleep quality, witnessed apnea, excessive daytime somnolence, and so forth) are also present. (Hypertension.
Key Words: hypertension, obesity ? sleep apnea syndromes ? sympathetic nervous system ? insulin resistance
Obesity: Prevalence and Association
The National Institutes of Health (NIH) and World Health
Organization (WHO) guidelines define individuals with body
mass index (BMI) ?25 as overweight and those with BMI
?30 as obese. By these criteria, the prevalence of overweight
and obesity are extremely high, approaching epidemic pro-
portions. For example, it is estimated that ?60% of men and
50% of women are currently overweight in the United States,
which represents more than 97 million adults.1Trend analy-
ses suggest that this epidemic continues to increase (Table).
The high prevalence of obesity represents a major public
health problem, predisposing to cardiac and vascular morbid-
ity and mortality. Most notably, epidemiologic data consis-
tently support a link between obesity and hypertension.2The
Framingham Heart Study suggests that 65% of the risk for
hypertension in women and 78% in men can be related to
obesity.3In some populations, an almost linear relation exists
between BMI and systolic/diastolic blood pressure.4How-
ever, the relation between obesity and hypertension is com-
plex and probably represents an interaction of racial, gender,
demographic, genetic, neurohormonal, and other factors. In
addition, upper body (android) obesity, especially in the
presence of increased visceral fat, is more strongly associated
with hypertension than lower body (gynoid) obesity.
Considering the significant impact of even modestly ele-
vated blood pressure on cardiovascular morbidity and mor-
tality,5it is not surprising that hypertensive cardiac and
vascular disease contributes very substantially to the high
cardiovascular morbidity associated with obesity. Therefore,
understanding the mechanisms of obesity-induced hyperten-
sion is important both for prevention and therapy. In this
review, we present evidence that obstructive sleep apnea
(OSA) might be an important mechanism underlying the
association between obesity and hypertension.
Sleep Apnea: Prevalence and Association
OSA is characterized by recurrent episodes of cessation of
respiratory airflow caused by upper airway inspiratory col-
lapse during sleep, with a consequent decrease in oxygen
saturation. Although its prevalence may vary in different
populations and age groups, it has been estimated that OSA
affects ?24% and 9% of middle-aged men and women,
respectively.6Moreover, the 5-year incidence of sleep-
disordered breathing in a community-based sample has re-
cently been found to be ?16% and 7.5% for mild-to-
moderate and for severe sleep-disordered breathing,
The evidence supporting the association between OSA and
chronic, long-standing hypertension is compelling and is
provided by several cross-sectional, longitudinal, and treat-
ment studies. Several reports have shown that the prevalence
of hypertension is greater in patients with OSA and vice
Received June 18, 2003; first decision July 10, 2003; revision accepted October 3, 2003.
From the Mayo Clinic, Rochester, Minn.
Correspondence to Virend K. Somers, MD, DPhil, Mayo Foundation, St Mary’s Hospital, DO-4-350, 1216 Second St SW, Rochester, MN 55902.
© 2003 American Heart Association, Inc.
Hypertension is available at http://www.hypertensionaha.org DOI: 10.1161/01.HYP.0000101686.98973.A3
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