title: Diurnal variation in vascular function: role of sleep.
abstract: Although vascular function is lower in the morning than afternoon, previous studies have not assessed the influence of prior sleep on this diurnal variation. The authors employed a semiconstant routine protocol to study the contribution of prior nocturnal sleep to the previously observed impairment in vascular function in the morning. Brachial artery vascular function was assessed using the flow-mediated dilation technique (FMD) in 9 healthy, physically active males (mean ± SD: 27 ± 9 yrs of age), at 08:00 and 16:00 h following, respectively, 3.29 ± .37 and 3.24 ± .57 h prior sleep estimated using actimetry. Heart rate and systolic and diastolic blood pressures were also measured. The data of the experimental sleep condition were compared with the data of the "normal" diurnal sleep condition, in which FMD measurements were obtained from 21 healthy individuals who slept only during the night, as usual, before the morning test session. The morning-afternoon difference in FMD was 1 ± 4% in the experimental sleep condition compared with 3 ± 4% in the normal sleep condition (p = .04). This difference was explained by FMD being 3 ± 3% lower in afternoon following the prior experimental sleep (p = .01). These data suggest that FMD is more dependent on the influence of supine sleep than the endogenous circadian timekeeper, in agreement with our previous finding that diurnal variation in FMD is influenced by exercise. These findings also raise the possibility of a lower homeostatic "set point" for vascular function following a period of sleep and in the absence of perturbing hemodynamic fluctuation.
authors.affiliation: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom. h.jones1@ljmu.ac.uk
authors.forename: Helen
authors.initials: H
authors.lastname: Jones
authors.forename: Nia C S
authors.initials: NC
authors.lastname: Lewis
authors.forename: Andrew
authors.initials: A
authors.lastname: Thompson
authors.forename: Kelly
authors.initials: K
authors.lastname: Marrin
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Green
authors.forename: Greg
authors.initials: G
authors.lastname: Atkinson
mesh_terms: D000293:Adolescent; D000328:Adult; D001808:Blood Vessels / Q000000981:diagnostic imaging / Q000294:innervation / Q000502:physiology*; D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000294:innervation / Q000502:physiology; D002318:Cardiovascular Diseases / Q000209:etiology / Q000503:physiopathology; D002940:Circadian Rhythm / Q000502:physiology*; D004730:Endothelium, Vascular / Q000502:physiology; D006801:Humans; D008297:Male; D008955:Models, Cardiovascular; D012890:Sleep / Q000502:physiology*; D014463:Ultrasonography; D014664:Vasodilation / Q000502:physiology; D014666:Vasomotor System / Q000502:physiology; D055815:Young Adult