To Dip or Not to Dip

Abstract

Abstract-That sleep is accompanied by a blood pressure decrease is well known; however, the underlying physiology deserves further investigation. The present study examines in healthy subjects 2 main questions: is this dipping actively evoked? and what are the consequences of nondipping for daytime blood pressure? Nocturnal blood pressure was extrinsically elevated in 12 sleeping subjects to mean daytime values by continuously infused phenylephrine. This nondipping significantly lowered morning blood pressure during rest and 3 hours after resuming physical activity compared with a control condition (isotonic saline). Neither muscle sympathetic nerve activity nor sensitivity of ␣-adrenoceptors was reduced. However, the set point for initiation of regulatory responses through the baroreflex was clearly shifted toward lower blood pressure levels. Our results support the hypothesis of an actively regulated central mechanism for blood pressure resetting and set point consolidation of the baroreflex during nighttime sleep. This is suggested by the fact that extrinsically induced nondipping induces sustained decrease in blood pressure during the following morning through an actively lowered baroreflex set point. (Hypertension.

Effects of Baroreflex Activation Therapy on Ambulatory Blood Pressure in Patients With Resistant Hypertension

“…35 Of all the indicators obtained during ABPM, night-time BP is the one that is best correlated with sympathetic nervous activity and prognosis. 25,36 For example, the ABPM substudy of the Anglo-Scandinavian Cardiac Outcome Trial (ASCOT) showed that night-time SBP is superior compared with office SBP in predicting stroke 37 or the Dublin outcome study showed that nocturnal BP is as an independent predictor of composite cardiovascular end points. 38 Herein, BAT significantly reduced night-time SBP and DBP by −9(−3 to [−15])/−5(−1 to [−9]) mm Hg after 6 months.…”

Adrenergic, Metabolic, and Reflex Abnormalities in Reverse and Extreme Dipper Hypertensives

“…[2][3][4][5][6][7][8][9][10][11][12] However, information is limited and contradictory on whether individuals with these different BP patterns display differences in the factors involved in cardiovascular control that may relate to and account for the different day-night BP changes. [13][14][15][16][17][18] This is particularly the case for a fundamental mechanism participating in day and night cardiovascular modulation such as the adrenergic nervous system. 19 The present study was aimed at addressing the above issue by using direct measurement of muscle sympathetic nerve activity (MSNA) via microneurography in untreated hypertensive patients whose belonging to the dipping, nondipping, extreme dipping, and reverse dipping pattern was confirmed by repeated ambulatory BP monitorings.…”

Antihypertensive medication prior to nocturnal sleep reduces the risk of new-onset type 2 diabetes in hypertensive patients: a role for slow-wave sleep?

“…Studies have shown that increased activity of the sympathetic nervous system (SNS) can alter human sleep. For example, in response to peripheral infusions of the α-adrenergic agonist phenylephrine which does not pass the blood-brain barrier, during first hours of nocturnal sleep, healthy normotensive volunteers are more prone to intermittent wakefulness and spend less time in slow-wave sleep (SWS) [3]. Experimental reductions of SWS and interruptions of sleep have recently been linked to impaired morning insulin sensitivity in healthy humans [4,5].…”