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This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 103/4/1332    most recent 00474.2007v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Zaregarizi, M. Articles by Atkinson, G. Search for Related Content PubMed PubMed Citation Articles by Zaregarizi, M. Articles by Atkinson, G.

Acute changes in cardiovascular function during the onset period of daytime sleep: comparison to lying awake and standing

¹Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom; ²Ministry of Health and Education, Tehran, Islamic Republic of Iran; and ³School of Psychology, Liverpool John Moores University, Liverpool, United Kingdom

Submitted 21 May 2007 ; accepted in final form 16 July 2007

The siesta habit is associated with a 37% reduction in coronary mortality, possibly because of reduced cardiovascular stress associated with daytime sleep. Whether the most important behavior is the daytime nap itself, a supine posture, or the expectancy of a nap is unknown. We present the first detailed description on healthy individuals of the acute changes in cardiovascular function during defined phases of the daytime sleep-onset period. These responses were compared with lying awake and standing. Following a night of restricted (4 h) sleep, nine healthy participants (aged 34 ± 5 yr) were allowed to sleep at 1400 for up to 1 h. Polysomnography was used to calculate three phases of daytime sleep onset: phase 1, a baseline period of relaxed wakefulness before lights out; phase 2, the period between lights out and onset of stage 1 sleep; and phase 3, the period between onsets of stages 1 and 2 sleep. Differences (means ± SD) in blood pressure, heart rate, and forearm cutaneous vascular conductance (CVC) between phases were analyzed. During the 9.7 ± 13.8 min of phase 2, systolic and diastolic blood pressure was 4.7 ± 4.5 and 3.6 ± 2.8 mmHg lower than baseline, whereas CVC was 9.5 ± 4.3% higher than baseline (P < 0.05). Subsequent changes in cardiovascular function during the sleep itself were trivial (P > 0.05). The above changes were not observed when subjects stood or laid supine in relaxed wakefulness for 1 h (P > 0.05). Our findings suggest that the period between lights out and sleep onset is associated with the largest acute reduction in blood pressure during one afternoon siesta.

blood pressure; heart rate; blood flow; polysomnography; napping