For patients who have resistant hypertension and obstructive sleep apnea, 3 months of treatment with continuous positive airway pressure significantly reduces mean and diastolic blood pressure and improves the nocturnal blood pressure pattern, according to a report published online Dec. 10 in JAMA.
These improvements are dose related, with mean blood pressure decreasing 1.3 mm Hg, systolic blood pressure decreasing 1.9 mm Hg, and diastolic blood pressure decreasing 1.0 mm Hg for every additional hour of CPAP use, said Dr. Miguel-Angel Martinez-Garcia of the respiratory department at Hospital Universitario y Politecnico La Fe, Valencia (Spain), and his associates.
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For patients who have resistant hypertension and obstructive sleep apnea, 3 months of treatment with continuous positive airway pressure significantly reduces mean and diastolic blood pressure and improves the nocturnal blood pressure pattern, according to the report.
"Obstructive sleep apnea is highly prevalent in patients with resistant hypertension, regardless of other confounding variables such as the presence of obesity, thus suggesting this subgroup of hypertensive patients is a potential worthwhile population for CPAP treatment," they said.
"International guidelines have pointed out that even minimal reductions in blood pressure levels (to the order of 2-3 mm Hg of systolic pressure) could have a clinically significant effect by greatly reducing subsequent cardiovascular mortality (between 6% and 8% for stroke and 4% and 5% for coronary heart disease)," Dr. Martinez-Garcia and his colleagues noted.
Previous studies have shown that CPAP produces clinically significant decreases in blood pressure levels, but all have had "significant methodological limitations such as small cohorts or lack of randomization." So Dr. Martinez-Garcia and his associates performed a large randomized multicenter clinical trial to assess the issue.
They identified 194 adults treated at 24 teaching hospitals across Spain who had resistant hypertension unrelated to known causes such as primary aldosteronism, renal artery stenosis, or renal insufficiency. Resistant hypertension was confirmed via 24-hour ambulatory blood pressure monitoring. The study subjects also had obstructive sleep apnea, which was confirmed by standard sleep studies.
These subjects were randomly assigned to receive CPAP (98 patients) or no intervention (96 patients who served as controls) while continuing their usual regimens of antihypertensive treatment. Approximately 69% of the subjects were men; the mean age was 56 years, the mean body mass index was 34.1, the mean number of antihypertensive drugs taken was 3.8, and the mean apnea-hypopnea index was 40.4 events per hour.
In the intention-to-treat analysis, after 3 months, the CPAP group achieved significantly greater decreases in 24-hour mean blood pressure and 24-hour mean diastolic blood pressure, and showed greater improvements during the night than during daytime. They also converted to more favorable nocturnal "dipper" and "riser" patterns in blood pressure, indicating decreased cardiovascular risk.
In the per-protocol analysis involving the 71 CPAP patients and 87 controls who adhered to the study protocol, these improvements were even more pronounced: The CPAP group showed a significant 4.4–mm HG decrease in 24-hour mean blood pressure, a 4.9–mm Hg decrease in systolic blood pressure, and a 4.1–mm Hg decrease in diastolic blood pressure (JAMA 2013 Dec. 10 [doi:10.1001/jama.2012.281250]).
At night, these figures were even better, with a 7.1–mm Hg decrease in systolic blood pressure and 4.1–mm Hg decrease in diastolic blood pressure. And again, the CPAP patients were more likely to convert to more favorable nocturnal "dipper" and "riser" patters in blood pressure.
There also was a positive linear correlation between the number of hours of CPAP use per night and the decrease in 24-hour mean blood pressure and diastolic blood pressure.
"Our results confirm that there is a clinically and statistically significant reduction in both 24-hour mean and diastolic blood pressure levels, especially during the night and in those patients with acceptable CPAP adherence," Dr. Martinez-Garcia and his associates said.
Further research is warranted to assess whether these benefits translate into better health outcomes in the long term, they added.
This study was supported by Philips Respironics, Sociedad Espanola de Neumologia, Instituto de Salud Carlos III, and Sociedad Valencia de Neumologia. No conflicts of interest were reported.