Patients with obstructive sleep apnea (OSA) and resistant hypertension who used continuous positive airway pressure (CPAP) had lower blood pressure over a 12-week period, according to a study published online Dec. 11 in JAMA.

Prior research has suggested that CPAP may reduce blood pressure, but whether the effect is observed in people with resistant hypertension is unclear.

“The objective of our study was to conduct a randomized, multicenter clinical trial to assess the effect of CPAP treatment on blood pressure values and nocturnal blood pressure patterns of patients with resistant hypertension and OSA,” explained the authors, led by Miguel-Angel Martinez-Garcia, MD, PhD, of University Hospital La Fe in Valencia, Spain.

They randomly assigned 194 patients with both resistant hypertension and OSA to receive either CPAP or no CPAP (control group) over a 12-week period between June 2009 and October 2011. Resistant hypertension was defined as an average systolic blood pressure (SBP) of 130 mm Hg or higher, a diastolic blood pressure (DBP) of 80 mm Hg or higher or both despite the use of at least three medications to control blood pressure. The primary outcome was the change in the ambulatory mean blood pressure in a 24-hour period. The investigators also assessed day and night SBP as well as changes in blood pressure patterns during the night.

At the start of the study, 25.8 percent of patients experienced at least a 10 percent decrease in average nocturnal blood pressure compared with diurnal blood pressure (the “dipper pattern”). In the group using CPAP for at least four hours per day, that percentage jumped to 72.4 percent.

Compared with controls, the decrease in 24-hour average blood pressure in the CPAP group was 3.1 mm Hg greater and the decrease in the 24-hour DBP was 3.2 mm Hg greater. The dipper pattern was greater in the CPAP group as well (35.9 percent vs. 21.6 percent).

While these findings suggested a short-term benefit of CPAP in this patient population, the authors noted that there should be additional research to determine whether any long-term effects exist.