Expecting an afternoon nap can reduce bloo...(nction of daytime sleep in healthy indiv...)
nction of daytime sleep in healthy individuals, comparing napping with other daytime activities such as standing and lying down without going to sleep.
Nap versus Conscious Rest
The researchers tested nine healthy volunteers (eight men, one woman) who did not routinely take afternoon naps. The volunteers attended the university laboratory on three separate afternoons after sleeping four hours the night before. The volunteers wore equipment that checked blood pressure, heart rate, and forearm cutaneous vascular conductance (which determines dilation of blood vessels).
During one afternoon session, the volunteer spent an hour resting, lying face-up in bed. During another session, the volunteer spent an hour relaxed, but standing. And in one session, the volunteer was allowed an hour to sleep, lying face-up. During the sleep stage, the researchers measured the volunteers different stages of sleep.
The session in which the volunteer was allowed to fall asleep was delineated into three phases:
- Phase 1: A five-minute period of relaxed wakefulness before lights were turned off (volunteers had been lying on the bed for a minimum of 15 minutes before this phase)
- Phase 2: The period between lights out and the onset of Stage 1 sleep (loss of some conscious awareness of the external environment)
- Phase 3: The period between the Stage 1 and the onset of Stage 2 sleep (conscious awareness of the external environment disappears)
Changes Found Only in Pre-Sleep
Researchers found a significant drop in blood pressure during the sleep trial, but not during the resting or standing trials. Whats more, this drop in blood pressure occurred mostly after lights out, just before the volunteer fell asleep.
This reduction in blood pressure may be one explanation for the lower cardiovascular mortality that some studies have found among people who habitually take siestas.
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| Contact: Christine Guilfoy cguilfoy@the-aps.org 301-634-7253 American Physiological Society Source:Eurekalert |
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