The study included 284 patients between ages 18 and 75 who visited hospitals in Brazil, Spain and Singapore to treat resistant hypertension. More than 83 percent of patients with resistant hypertension also had obstructive sleep apnea. That included nearly 32 percent with severe obstructive sleep apnea, 25.7 percent with moderate and 31.7 percent mild forms of the condition.
Over 86 percent of men in the study were likely to have obstructive sleep apnea compared to 76 percent of women, though men were twice as likely to have a severe form of the condition.
The ambulatory blood pressure, measurement of pressure levels in 24-hour intervals, increased as the sleep apnea got more severe. Patients with severe obstructive sleep apnea had blood pressure readings 5.72 mmHg higher than those with normal obstructive sleep apnea.
The researchers say the cardiovascular risk is greater for those with high blood pressure at night.
However, they caution that the findings may not apply to the average person with high blood pressure.
“Considering the high prevalence of OSA in resistant hypertensive subjects and findings from previous studies which show that treating OSA with CPAP can lower blood pressure, clinicians should consider performing a sleep study in patients with resistant hypertension,” Dalmases Cleries said.