The Effects of Continuous Positive Airway Pressure on Prehypertension and Masked Hypertension in Men With Severe Obstructive Sleep Apnea
Obstructive sleep apnea and hypertension are common conditions that frequently coexist. Continuous positive airway pressure (CPAP) reduces blood pressure in patients with obstructive sleep apnea and sustained hypertension. However, the impact of CPAP on patients with obstructive sleep apnea and prehypertension and masked hypertension, conditions associated with increased cardiovascular risk, is unknown.
Hypertension remains a major cause of cardiovascular complications worldwide with a prevalence that increases in parallel with increasing age. The terminology and thresholds to define abnormal blood pressure have changed overtime, reflecting the progressive awareness that intervention in the precursors of hypertension are effective in reducing future cardiovascular risk. The term “prehypertension” was introduced by the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure and was defined as a systolic blood pressure (BP) of 120 to 139 mm Hg and a diastolic BP of 80 to 89 mm Hg. Although prehypertension is not considered a special category of hypertension, it is frequently a precursor of sustained hypertension and increasingly associated with an excess morbidity and mortality from cardiovascular disease. Similarly, masked hypertension, a condition characterized by normal office BP and abnormal 24-hour ambulatory BP (ABPM), may also be a precursor of sustained hypertension and is also an independent cardiovascular risk factor when compared with true normotensive subjects. Despite this evidence, the impact of recognition and treatment of comorbid conditions on BP in patients with prehypertension and masked hypertension remains poorly understood.
Obstructive sleep apnea (OSA) is characterized by repetitive episodes of upper airway obstruction during sleep resulting in intermittent hypoxia and arousals from sleep. OSA is common in the general population, and the prevalence is strikingly high among patients with sustained hypertension (approximately 50%). There is growing evidence that OSA participates in the genesis of hypertension through several mechanisms, including sympathetic overactivation, oxidative stress, systemic inflammation, and increased arterial stiffness. The treatment of OSA with continuous positive airway pressure (CPAP) is able to reduce BP in patients with OSA and sustained hypertension.8 However, patients with OSA frequently present several comorbid conditions, and the treatment of OSA rarely normalizes BP to the point that antihypertensive medications can be discontinued. Moreover, the effects of CPAP on BP may be extremely dependent on the BP status at study entry and tend to be higher in patients with high levels of BP,9 reaching minimal or no effects in patients with normal BP.
The association among OSA, prehypertension, and masked hypertension has gained recent interest. To the best of our knowledge, no studies have attempted to study prehypertension in patients with OSA. On the other hand, at least 2 independent studies showed that masked hypertension is common among patients with OSA and apparent normal BP when ABPM is performed. This raises the question whether OSA treatment can reduce or even normalize BP in patients with prehypertension and masked hypertension. Therefore, this randomized study was designed to evaluate the impact of the treatment of OSA with CPAP on BP in patients with severe OSA and no overt comorbid conditions with prehypertension and/or masked hypertension. Some of the results of this study have been previously reported in the form of an abstract.