Sleep Apnea and Hypertension

What is hypertension?

Hypertension is elevated blood pressures when measured in a resting state on several measurements. According to the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (called JNC7 for short) the following lists the classification of hypertension:

	Systolic BP (mmHg)	Diastolic BP (mmHg)
Normal	<120 and	<80
Prehypertension	120-139 or	80-89
Stage 1	140-159 or	90-99
Stage 2	≥ 160 or	≥ 100

Standard treatment goals of hypertension are BP < 140/90 mmHg or < 130/80 mmHg in patients with diabetes or chronic kidney disease.

What does sleep apnea have to do with hypertension?

Sleep apnea has been associated with hypertension. The Sleep Heart Heath Study (JAMA 2000; 283: 1829) analyzed 6,132 subjects and found that patients with severe sleep apnea (AHI > 30/hr) were 1.37 times as likely to have hypertension compared to subjects without sleep apnea. The Wisconsin Sleep Cohort Study (Arch Intern Med 1997; 157: 1746) assessed 1,069 subjects and demonstrated a 3.1 times increased chance of having hypertension in the severe sleep apnea group compared to those without sleep apnea. A follow up to this study (N Engl J Med 2000; 342: 1378) revealed that people with moderate or severe sleep apnea were 2.89 times as likely to develop hypertension over 4-8 yrs of follow up.

How does treatment with CPAP affect blood pressure?

All of the studies that have addressed this question are small. Here are summaries of several of the larger studies: (skip to conclusions if the details bore you)

Faccenda (Am J Resp Crit Care Med 2001;163:344) studied 68 patients with sleep apnea and normal blood pressure. The patients were randomized to CPAP or oral placebo pill. They were treated for 4 weeks and then crossed over (i.e. if they were using CPAP they were switched to the placebo and vice-versa). Blood pressure was measured continuously for the last 48 hrs of treatment. There was a significant decrease in diastolic blood pressure of 1.5 mmHg but not a significant change in systolic blood pressure in all patients. For patients who used the CPAP for at least 3.5 hrs per night, there was a decrease in diastolic BP of 1.9 mm Hg. For patients who had a 4% drop in oxygen level on average 20 times per hour (an indicator of increasing severity of sleep apnea), there was a significant decrease in systolic (4.0 mm Hg) and diastolic (5.0 mm Hg) BPs.

Pepperell (Lancet 2001;359:204) studied 118 men with sleep apnea and normal BP. The patients were randomized to therapeutic CPAP (pressure demonstrated to control sleep apnea) vs sham CPAP (set to 1 cm H2O pressure – too low to control sleep apnea). After 4 weeks of treatment, the patients underwent 24 hr measurement of BP. The therapeutic CPAP group had a decrease in average BP of 2.5 mm Hg while it increased by 0.8 mm Hg in the sham CPAP group. Additionally, the systolic BP decreased by 3.4 mmHg and the diastolic BP decreased by 3.3 mm Hg in the therapeutic vs sham CPAP groups.

Dimsdale (Hypertension 2000; 35:144) studied 39 patients with sleep apnea. The patients were treated with therapeutic or ineffective CPAP for 1 week and had BP measurements at the baseline and conclusion of the study. Both groups had a decrease in daytime average BP (greater decrease in the therapeutic CPAP group, but not statistically significant difference due to small numbers) while nighttime average BP decreased significantly in the therapeutic but not sham CPAP groups.

Hla (Chest 2002;122:1125) investigated 24 men with untreated hypertension. They were assessed for sleep apnea with a sleep study and 14 men had an apnea hypopnea index (AHI) > 5 (at least mild sleep apnea) and 10 had a normal AHI (<5/hr). Patients with sleep apnea were treated with a CPAP pressure to control sleep apnea. Patients without sleep apnea were treated with CPAP 5 cm H2O (low although not insignificant pressure). The CPAP was used for 3 weeks. 24 hr ambulatory BP monitoring was performed at the baseline, during CPAP and after CPAP treatment. The patients with sleep apnea treated with therapeutic CPAP had a greater decrease in night-time BP (-7.8 vs -5.3 mm Hg). Daytime BP differences did not reach statistical significance but there was a trend toward lower systolic BPs (-2.7 vs +0.4 mmHg) and diastolic BPs (-2.3 v -1.7 mm Hg) in the sleep apnea group treated with therapeutic CPAP.

Logan (Eur Resp J 2003; 21:241) studied 11 patients with difficult to control hypertensions and sleep apnea. The patients remained hypertensive despite at least 3 blood pressure medications. All patients were treated with therapeutic CPAP and there was not a control group in this study. Average BP decreased by 11 mmHg after 2 months of treatment.

Becker (Circulation 2003;107:68) studied 32 patients with moderate to severe sleep apnea. 23/32 patients were previously diagnosed with hypertension and 15 were receiving medicatiosn to control their BP. The patients were randomly assigned to 9 weeks of treatment with therapeutic CPAP or subtherapeutic CPAP. Continuous BP monitoring was performed with a finger cuff measurement (which the authors say does not wake people up like the other BP monitoring devices do) before and during treatment. Baseline BPs were 135.9/83.4 in the therapeutic CPAP group and 136.2/81.1 in the subtherapeutic group. The group treated with therapeutic CPAP had a 9.9 mm Hg decrease in average blood pressure while the group treated with subtherapeutic CPAP had an increase in average BP of 0.6 mmHg. Systolic BP decreased by 9.5 mmHg and diastolic BP decreased by 10.3 mmHg in the therapeuticCPAP group.

Campos-Rodriguez (Chest 2006;129:1459) investigated 72 patients with sleep apnea and hypertension who were treated with therapeutic CPAP or subtherapeutic CPAP (applied as CPAP < 2 cm H2O – very low pressure). All patients were receiving medications to control their blood pressure, with the average need for 2 different BP medications. Average BPs at baseline were 131.9/78.4 mm Hg in the therapeutic CPAP group and 130.4/77.6 in the subtherapeutic CPAP group. This study did not reveal any difference in blood pressures in the 2 groups.

Conclusions about treatment:

· There is a small decrease in BP in patients with normal BPs when they use CPAP.

· Patients with hypertension may have up to a 10 mmHg decrease in pressure when using CPAP to control sleep apnea; however there is conflicting data.

· Patients already being treated with medications for hypertension may not have a significant decrease in blood pressure when using CPAP if BP is already well controlled; however people with difficult to control BP appear to have a significant decrease in BP when using CPAP.

Larger studies are required help clarify this question as all of the studies are small.