Sleepers Versus Nonsleepers

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There is growing evidence that an elevated nocturnal blood pressure is associated with an adverse cardiovascular outcome. In the Dublin Outcome Study, for each 10-mm Hg increase in mean nighttime systolic blood pressure, the mortality risk increased by 21%.1 At present, ambulatory blood pressure measurement is the only technique that permits close examination of the circadian profile and identification of patterns that may be associated with risk. Much happens to the cardiovascular system at nighttime, especially in relation to blood pressure. The patterns of nocturnal blood pressure–nocturnal hypertension, nocturnal hypotension, dipping and nondipping, reverse dipping, and autonomic failure–have been largely ignored in clinical practice. Many studies evaluating morbidity and dipping status have supported the concept that a diminished nocturnal blood pressure fall is associated with a worse prognosis.2 However, despite compelling evidence that changes in nighttime blood pressure may hold many secrets that, if unlocked, might benefit the clinical management of hypertension, there has been reluctance to focus on nocturnal blood pressure both clinically and in hypertension research.3 The nocturnal period of the 24-hour blood pressure profile, which is surprisingly complex, can be divided into a number of windows in which discrete phenomena may occur. These windows are the retiring (or perhaps more aptly named vesperal) window, the nighttime (or basal) window during which sleep is most likely, and the preawakening (or matinal) window, which precedes rising. In the normal individual there is a decline in blood pressure in the vesperal window from daytime levels of blood pressure to reach a plateau during the basal window (the “dipping” pattern), with a modest rise in the matinal window to regain daytime levels of blood pressure.4 In hypertensive patients (or …