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BP increases with severity of OSA in resistant hypertension

Obstructive sleep apnea is highly prevalent and more severe disease appears to be associated with higher blood pressure among patients with resistant hypertension, a recent study suggests.

“We believe that OSA plays an important role in the pathogenesis and prognosis of patients with resistant hypertension,” Mireia Dalmases Cleries, MD, a pulmonologist and sleep researcher at the Hospital Universitari Arnau de Vilanova, said in a press release. “Our study shows a dose-response association between OSA severity and blood pressure, especially during the nighttime period.”

Dalmases Cleries and colleagues evaluated 284 patients with resistant hypertension from three countries recruited between April 2016 and July 2018 as an ancillary study to the SARAH study — a multicenter, international, prospective, observational cohort study measuring the effect of OSA and CPAP on cardiovascular outcomes among patients with resistant hypertension. Only patients aged 18 to 75 years with a diagnosis of resistant hypertension confirmed via 24-hour ambulatory BP monitoring were included. Patients with life expectancy less than 1 year, undergoing current CPAP treatment or with resistant hypertension secondary to an endocrinological cause, drug treatment, renal artery stenosis, intracranial tumors or aortic coarctation were excluded.

Of the patients included in the study, 34 underwent polysomnography and 250 underwent cardiorespiratory polygraphy to diagnose OSA. OSA was categorized as mild, moderate or severe based on apnea-hypopnea index (AHI) scores.

Ambulatory BP monitoring was measured according to international guidelines, whereas office BP was evaluated by averaging three systolic and diastolic BP recordings taken at 5-minute intervals after patients had been seated for a minimum of 5 minutes. BP was classified as controlled if the patient had an average 24-hour ambulatory BP less than 130 mm Hg/80 mm Hg or uncontrolled if the patient’s BP had an average 24-hour ambulatory measurement of 130 mm Hg/80 mm Hg or higher.

Most patients (83.5%) had OSA, defined as AHI of five events or more per hour. Of these, 31.7% of cases were mild, 25.7% were moderate and 26.1% were severe. Patients with severe OSA had higher BP than patients with mild or moderate OSA or patients without OSA overall and were more than twice as likely to have nocturnal hypertension when compared with patients without severe OSA (OR = 2.7; 95% CI, 1.15-6.43).

Severe OSA prevalence was also higher among patients with uncontrolled BP compared with patients with controlled BP, but the difference was not statistically significant.

“This could be related to the fact that the greatest impact of OSA on BP has been observed on nocturnal pressure and that the nighttime period only represents approximately one-third of the 24-hour [measurements],” the researchers wrote. “The results suggest that the decision to explore OSA in subjects with resistant hypertension should not be based on the BP control parameters proposed in the hypertension guidelines and that it could be especially important to assess OSA in subjects with resistant hypertension who have high BP values at nighttime even if they have values in the normal ranges for the 24-hour measurements.” – by Eamon Dreisbach

Disclosures: Dalmases Cleries reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.