The Silent Partner in the Sleep Apnea–Hypertension Relationship
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See related article, pp 1264–1270
Evidence implicating obstructive sleep apnea (OSA) in blood pressure elevation is compelling, such that OSA is acknowledged as a risk factor in the major guidelines for prevention and management of hypertension.1,2 Nevertheless, not every patient with OSA will develop comorbid hypertension. Traditional markers of disease severity, such as apnea–hypopnea index and degree of nocturnal desaturation, as well as coexisting conditions, including obesity and old age, have been implicated as determinants of enhanced vulnerability.3 More recently, excessive daytime sleepiness (EDS), a common but not pervasive symptom of OSA, has emerged as a nonconventional indicator for identifying high-risk OSA subjects. However, the available literature on the prognostic role of hypersomnolence for clinical outcomes, including hypertension, is controversial.4,5 This discrepancy may be ascribed to the various approaches used to determine EDS, as suggested by Ren et al6 in this issue of Hypertension.
These investigators examined the association between prevalent hypertension and EDS in a large, well-characterized Chinese population. The sample consisted of referrals to the sleep clinic for suspected OSA, which was assessed by in-laboratory polysomnography. The use of the gold standard diagnostic method for OSA, in lieu of questionnaires or portable monitors, is a strength of the article. Another important feature is the dual assessment of sleepiness performed in the study. All subjects completed a self-report measure (Epworth Sleepiness Scale7) and a sleep laboratory test (Multiple Sleep Latency Test [MSLT]8) and were then classified based on the average sleep latency (the time taken to fall asleep) exhibited at the MSLT, as an index of EDS. The MSLT consists of 4 to 5 nap opportunities spread across the …