Role of melatonin in blood pressure regulation: An adjunct anti-hypertensive agent

The early hours of the morning after awakening are associated with an increased frequency of events such as myocardial infarction and ischemic stroke. The triggering mechanisms for these events are not clear. We investigated whether autonomic changes occurring during sleep, particularly rapid-eye-movement (REM) sleep, contribute to the initiation of such events. We measured blood pressure, heart rate, and sympathetic-nerve activity (using microneurography, which provides direct measurements of efferent sympathetic-nerve activity related to muscle blood vessels) in eight normal subjects while they were awake and while in the five stages of sleep. The mean (+/- SE) amplitude of bursts of sympathetic-nerve activity and levels of blood pressure and heart rate declined significantly (P < 0.001), from 100 +/- 9 percent, 90 +/- 4 mm Hg, and 64 +/- 2 beats per minute, respectively, during wakefulness to 41 +/- 9 percent, 80 +/- 4 mm Hg, and 59 +/- 2 beats per minute, respectively, during stage 4 of non-REM sleep. Arousal stimuli during stage 2 sleep elicited high-amplitude deflections on the electroencephalogram (called K complexes), which were frequently associated with bursts of sympathetic-nerve activity and transient increases in blood pressure. During REM sleep, sympathetic-nerve activity increased significantly (to 215 +/- 11 percent; P < 0.001) and the blood pressure and heart rate returned to levels similar to those during wakefulness. Momentary restorations of muscle tone during REM sleep (REM twitches) were associated with cessation of sympathetic-nerve discharge and surges in blood pressure. REM sleep is associated with profound sympathetic activation in normal subjects, possibly linked to changes in muscle tone. The hemodynamic and sympathetic changes during REM sleep could play a part in triggering ischemic events in patients with vascular disease.

Research associates short (and to a lesser extent long) sleep duration with obesity, diabetes, and cardiovascular disease; and although 7-8 h of sleep seems to confer the least health risk, these findings are often based on non-representative data. We hypothesize that short sleep ( 8 h) are positively associated with the risk of obesity, diabetes, hypertension, and cardiovascular disease; and analyze 2004-2005 US National Health Interview Survey data (n=56,507 observations, adults 18-85) to test this. We employ multilevel logistic regression, simultaneously controlling for individual characteristics (e.g., ethnoracial group, gender, age, education), other health behaviors (e.g., exercise, smoking), family environment (e.g., income, size, education) and geographic context (e.g., census region). Our model correctly classified at least 76% of adults on each of the outcomes studied, and sleep duration was frequently more strongly associated with these health risks than other covariates. These findings suggest a 7-8 h sleep duration directly and indirectly reduces chronic disease risk. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

It remains uncertain whether abnormal dipping patterns of nocturnal blood pressure influence the prognosis for stroke. We studied stroke events in 575 older Japanese patients with sustained hypertension determined by ambulatory blood pressure monitoring (without medication). They were subclassified by their nocturnal systolic blood pressure fall (97 extreme-dippers, with >/=20% nocturnal systolic blood pressure fall; 230 dippers, with >/=10% but /=0% but <10% fall; and 63 reverse-dippers, with <0% fall) and were followed prospectively for an average duration of 41 months. Baseline brain magnetic resonance imaging (MRI) disclosed that the percentages with multiple silent cerebral infarct were 53% in extreme-dippers, 29% in dippers, 41% in nondippers, and 49% in reverse-dippers. There was a J-shaped relationship between dipping status and stroke incidence (extreme-dippers, 12%; dippers, 6.1%; nondippers, 7.6%; and reverse-dippers, 22%), and this remained significant in a Cox regression analysis after controlling for age, gender, body mass index, 24-hour systolic blood pressure, and antihypertensive medication. Intracranial hemorrhage was more common in reverse-dippers (29% of strokes) than in other subgroups (7.7% of strokes, P=0.04). In the extreme-dipper group, 27% of strokes were ischemic strokes that occurred during sleep (versus 8.6% of strokes in the other 3 subgroups, P=0.11). In conclusion, in older Japanese hypertensive patients, extreme dipping of nocturnal blood pressure may be related to silent and clinical cerebral ischemia through hypoperfusion during sleep or an exaggerated morning rise of blood pressure, whereas reverse dipping may pose a risk for intracranial hemorrhage.