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To dip or not to dip: on the physiology of blood pressure decrease during nocturnal sleep in healthy humans
Friedhelm Sayk1, Christoph Becker, Christina Teckentrup
1Clinic for Internal Medicine I, University Hospital of Schleswig-Holstein, Luebeck, Germany.
Hypertension (Dallas, Tex. : 1979)
|March 14, 2007
Summary
Sleep actively lowers blood pressure via a central baroreflex mechanism. Disrupting this "dip" (nondipping) results in lower morning blood pressure, indicating an actively regulated process.
Area of Science:
- Cardiovascular Physiology
- Sleep Medicine
- Baroreflex Regulation
Background:
- Nocturnal blood pressure dipping is a known phenomenon.
- The precise physiological mechanisms driving this blood pressure decrease during sleep require further investigation.
Purpose of the Study:
- To determine if nocturnal blood pressure dipping is actively evoked.
- To investigate the consequences of impaired blood pressure dipping (nondipping) on subsequent daytime blood pressure.
Main Methods:
- Healthy subjects underwent controlled phenylephrine infusion during sleep to prevent normal blood pressure dipping.
- Nocturnal blood pressure, muscle sympathetic nerve activity, and alpha-adrenoceptor sensitivity were monitored.
- Baroreflex set point was assessed under control (saline infusion) and experimental (phenylephrine infusion) conditions.
Main Results:
- Extrinsically induced nondipping significantly lowered morning blood pressure compared to controls.
- Muscle sympathetic nerve activity and alpha-adrenoceptor sensitivity remained unchanged.
- The baroreflex set point was shifted to lower blood pressure levels during nondipping.
Conclusions:
- Results support an actively regulated central mechanism for blood pressure resetting during sleep.
- An actively lowered baroreflex set point contributes to sustained morning hypotension following induced nondipping.
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