Obstructive Sleep Apnea and Hypertension

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Obstructive Sleep Apnea and Hypertension

• Christine Won, M.D.
• Stanford Sleep Disorders Center

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Objectives

• Hypertension
• Definition
• Risk Factors
• Significance
• Causes
• Treatment
• Obstructive Sleep Apnea
• Association with Hypertension
• Physiology
• Causes
• Treatment
• Other Cardiovascular Diseases

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Definition of Hypertension

• Normal blood pressure systolic lt120 mmHg and
  diastolic lt80
• Pre-hypertension systolic 120-139 or diastolic
  80-89
• Hypertension 
• Stage 1 systolic 140-159 or diastolic 90-99
• Stage 2 systolic 160 or diastolic 100

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Prevalence of Hypertension
Hajjar, I, Kotchen, TA. JAMA 2003 290199.
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White-Coat Hypertension
Mancia, G, Parati, G, Pomidossi, G, et al,
Hypertension 1987 9209
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Risk Factors for Hypertension

• More common and more severe in blacks
• It is likely that increased salt intake is a
  necessary but not sufficient cause for
  hypertension
• Excess alcohol intake increases risk
• High cholesterol may also associated with the
  development of hypertension
• Hypertension may be more common among those with
  certain personality traits, such as hostile
  attitudes and time urgency/impatience

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Obesity and Hypertension

• Obesity is associated with an increased risk of
  hypertension, and weight gain appears to be a
  main determinant of the rise in blood pressure
  that is commonly seen with aging
• Weight loss improves blood pressure

Stevens, VJ, Corrigan, SA, Obarzanek, E, et al,
Arch Intern Med 1993 153849
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Why is Hypertension Important?

• Hypertension is associated with a number of
  serious adverse effects
• The likelihood of developing these complications
  varies with the blood pressure
• The increase in risk begins as the blood pressure
  rises above 110/75 mmHg and, at any blood
  pressure, is importantly affected by the presence
  or absence of other risk factors

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Why is Hypertension Important?

• Premature cardiovascular disease
• Coronary heart disease
• Heart failure
• Stroke
• Intracerebral hemorrhage
• Chronic renal insufficiency and end-stage renal
  disease
• Acute, life-threatening emergency

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What Causes Hypertension?

• Increased sympathetic neural activity
• Increased angiotensin II activity and
  mineralocorticoid excess
• Reduced adult nephron mass
• may be related to genetic factors, intrauterine
  disturbance (eg, hypoxia, drugs, nutritional
  deficiency), and post-natal environment (eg,
  malnutrition, infections)
• Hypertension is twice as common in those who have
  hypertensive parents genetic factors account for
  approximately 30 of the variation in blood
  pressure

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Benefit of Treating Hypertension

• Antihypertensive therapy has been associated with
  40 percent reduction in stroke 25 percent in
  myocardial infarction and more than 50 percent
  in heart failure
• It is estimated that control of hypertension to
  below 140/90 mmHg could, in men and women,
  prevent 19 and 31 percent of coronary heart
  disease events

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Lifestyle modifications in the management of
hypertension
The Seventh Report of the Joint National
Committee on Prevention, Detection, Evaluation,
and Treatment of High Blood Pressure, JAMA 2003
2892560
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Obstructive Sleep Apnea and Hypertension

• Wisconsin Sleep Cohort Study
• Dose-dependent relationship between severity of
  sleep apnea and risk of developing hypertension
• Odds for developing hypertension during a 4-8
  year follow-up period compared to subjects with
  no apneas or hypopneas was 2.0 if AHI was 5-15,
  and 3.0 if AHIgt15
• The Sleep Heart Health Study
• A cross-sectional analysis of a large
  community-based multi-center population showed an
  increase in odds of 1.4 for hypertension when AHI
  gt 30 compared to those with AHI lt 1.5
• The Nurses Health Study
• Increase in risk of 1.6 for the development of
  hypertension over an 8-year follow-up period in
  regular snorers compared to non-snorers

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The Relationship between Obstructive Sleep Apnea
and Hypertension

• The odds of having hypertension is 37 greater in
  persons with obstructive sleep apnea
• The odds of having hypertension is 46 greater in
  those who spend greater percentage of sleep time
  below 90 oxygen saturation

Nieto, F. J. et al. JAMA 20002831829-1836
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The Relationship between Obstructive Sleep Apnea
and Hypertension

• Compared to those with AHI0, the odds of having
  hypertension was 42 greater if AHI was 0.1-5, 2x
  greater if AHI was 5-15, and almost 3x greater if
  AHI was more than 15 per hour

Peppard et al. NEJM. 2000 3421378-1384
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Obstructive Sleep Apnea Physiology
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Obstructive Sleep Apnea Physiology
www.qeok.com/lung-cancer/asbestosis-picture.jpg
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Obstructive Sleep Apnea and Cardiovascular Effects

• EEG arousals
• Fragmented sleep
• Increased sympathetic activity

• Obstructive Apnea
• Negative Intrathoracic Pressure (Mueller
  Maneuver)
• Hypoxia
• Hypercapnia

• Resumption of breathing
• Labile blood pressure

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Overnight Polysomnogram in a Patient with
Obstructive Sleep Apnea
Tilkian AG, Guilleminault C. Ann Intern Med. 1976
Dec85(6)714-9
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The Sympathetic System

• Many early studies demonstrated abnormal
  autonomic activity in both animal models and in
  humans with obstructive sleep apnea
• Increased norepinephrine levels
• Increased muscle sympathetic nerve activity

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Sympathetic System Muscle Nerve Activity

• Compared muscle sympathetic nervous activity
  (MSNA) of blood vessels in untreated and treated
  OSA at baseline and after 1, 6, 12 months of CPAP
• MSNA was similar during repeated measurements in
  the untreated group
• In contrast, MSNA decreased significantly over
  time in patients treated with CPAP

Narkiewicz et al. Circulation 19991002332-2335
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Sympathetic System Norepinephrine

• 24-hr urinary NE increased 45 in apneic (RDIgt20)
  compared to non-apneic patients.
• CPAP treatment lowered daytime plasma NE levels
  by 23 Placebo had no effect on NE levels

Dimsdale et al, Sleep 199518377-81
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Treating Obstructive Sleep Apnea

• Several trials have demonstrated improved
  systolic and diastolic blood pressures with both
  short-term and long-term CPAP use
• Regular CPAP use has also shown to improve blood
  pressure in patients with refractory hypertension
  who were requiring three or more antihypertensive
  medications

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• The seventh Joint National Committee on
  Prevention, Detection, Evaluation, and Treatment
  of High Blood Pressure recommends evaluating for
  and treating obstructive sleep apnea in adults
  with hypertension

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Obstructive Sleep Apnea and other Cardiovascular
Diseases
www.rjmatthewsmd.com/Definitions/img/osa-fig3.gif
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Summary

• Hypertension is a serious disease that affects
  many people
• Scientific evidence for a link between
  obstructive sleep apnea and hypertension is
  compelling
• Sleep apnea is thought to contribute to
  hypertension by increasing sympathetic nervous
  system activity and causing vascular dysfunction
• Animal studies have demonstrated that sleep apnea
  can cause hypertension
• Human epidemiological studies confirm that
  untreated sleep apnea increases the risk of
  having hypertension

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Summary

• CPAP stabilizes the upper airway, preventing
  collapse and the acute cardiovascular and
  hemodynamic consequences of obstructive sleep
  apnea
• CPAP applied over several weeks reduces both
  systolic and diastolic blood pressure by 10 mm
  Hg. These reductions are predicted to reduce
  stroke risk by 56 and coronary heart disease
  event risk by 37
• The United States National Heart, Lung, and Blood
  Institute now recognizes sleep apnea as a
  significant and reversible cause of hypertension

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Thank You