In patients with high blood pressure resistant to treatment who also have obstructive sleep apnea (OSA), the more severe their OSA, the higher their blood pressure, according to new research published in the Annals of the American Thoracic Society.
Investigators at the Hospital Universitari Arnau de Vilanova, in Lleida, Spain, looked at 284 patients, ages 18 to 75, who were treated at hospitals in three countries—Spain, Singapore, and Brazil—for resistant hypertension. Of all patients with high blood pressure, those with resistant hypertension, which requires three or more drugs to control, are at greatest risk for a heart attack or other cardiovascular event.
“We believe that OSA plays an important role in the pathogenesis and prognosis of patients with resistant hypertension,” said senior author Mireia Dalmases Cleries, MD, a pulmonologist and sleep researcher. “Our study shows a dose-response association between OSA severity and blood pressure, especially during the nighttime period.”
The study also found:
- 83.5% of patients with resistant hypertension had OSA, including 31.7% with mild OSA, 25.7% with moderate OSA and 31.5% with severe OSA.
- OSA was slightly more likely in men than women: 86.3% vs. 76%; however, the men were twice as likely to have severe OSA.
- As the severity of OSA increased, ambulatory blood pressure increased, particularly at night. The average nighttime ambulatory blood pressure was 5.72 mmHg higher in those with severe OSA compared to those without OSA.
According to the authors, high blood pressure at night is a stronger predictor of cardiovascular risk than those whose blood pressure is high during the day. The authors said that because the study was not a randomized, controlled trial it could not prove cause and effect. The authors also note that because only patients with resistant hypertension were included in the study, the findings cannot be generalized to other patients with high blood pressure.
Dr. Dalmases Cleries said that, considering the high prevalence of OSA in patients with resistant hypertension and findings from previous studies that show treating OSA with CPAP can lower blood pressure, clinicians should consider performing a sleep study in patients with resistant hypertension.