Obstructive Sleep Apnea and Hypertension
Christine Won, M.D.Stanford Sleep Disorders Center
Objectives Hypertension
Definition Risk Factors Significance Causes Treatment
Obstructive Sleep Apnea Association with Hypertension Physiology Causes Treatment Other Cardiovascular Diseases
Definition of Hypertension
Normal blood pressure: systolic <120 mmHg and diastolic <80
Pre-hypertension: systolic 120-139 or diastolic 80-89
Hypertension: Stage 1: systolic 140-159 or diastolic 90-
99Stage 2: systolic 160 or diastolic 100
Hajjar, I, Kotchen, TA. JAMA 2003; 290:199.
Prevalence of Hypertension
Mancia, G, Parati, G, Pomidossi, G, et al, Hypertension 1987; 9:209
White-Coat Hypertension
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
Stevens, VJ, Corrigan, SA, Obarzanek, E, et al, Arch Intern Med 1993; 153:849
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
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
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
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
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
Modification Recommendation Approximate SBP reduction
Weight reduction
Maintain normal body weight (BMI 18.5 to 24.9 kg/m2)
5-20 mmHg per 10-kg weight loss
Adopt DASH eating plan
Consume a diet rich in fruits, vegetables, and low-fat dairy products with a reduced content of saturated and total fat
8 to 14 mmHg
Dietary sodium reduction
Reduce dietary sodium intake to no more than 100 meq/day (2.4 g sodium or 6 g sodium chloride)
2 to 8 mmHg
Physical activity Engage in regular aerobic physical activity such as brisk walking (at least 30 minutes per day, most days of the week)
4 to 9 mmHg
Moderation of alcohol consumption
Limit consumption to no more than 2 drinks per day in most men and no more than 1 drink per day in women and lighter-weight persons
2 to 4 mmHg
The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure, JAMA 2003; 289:2560
Lifestyle modifications in the management of hypertension
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 AHI>15
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 > 30 compared to those with AHI < 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
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 2000;283:1829-1836
Peppard et al. NEJM. 2000; 342:1378-1384
The Relationship between Obstructive Sleep Apnea and Hypertension
Compared to those with AHI=0, 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
Obstructive Sleep Apnea: Physiology
Obstructive Sleep Apnea: Physiology
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Obstructive Sleep Apnea and Cardiovascular Effects
Obstructive Apnea• Negative Intrathoracic
Pressure (Mueller Maneuver)
• Hypoxia• Hypercapnia
Resumption of breathing
• Labile blood pressure
EEG arousals• Fragmented sleep• Increased sympathetic activity
Tilkian AG, Guilleminault C. Ann Intern Med. 1976 Dec;85(6):714-9
Overnight Polysomnogram in a Patient with Obstructive Sleep Apnea
EEG
EOG
EKG
SBP
PAP
SAO2
RESP
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
Narkiewicz et al. Circulation 1999;100:2332-2335
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
Sympathetic System: Norepinephrine
Dimsdale et al, Sleep 1995;18:377-81
24-hr urinary NE increased 45% in apneic (RDI>20) compared to non-apneic patients.
CPAP treatment lowered daytime plasma NE levels by 23%; Placebo had no effect on NE levels
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
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
Obstructive Sleep Apnea and other Cardiovascular Diseases
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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
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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