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

Thank You