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