title: Heart-rate variability in women during 40-hour prolonged wakefulness.
abstract: Heart-rate variability patterns of 18 women during a 40-h constant routine of prolonged wakefulness under controlled laboratory conditions were analyzed. The authors tested the circadian timing of the autonomic nervous system and the relationship between the sympathetic and vagal branches in women with both a functional disorder of vascular regulation (main symptom: cold hands and feet) and prolonged sleep onset and controls without these symptoms. Spectral analysis of R-R intervals during paced breathing episodes revealed significantly lower power values in the high-frequency band (HF; 0.15-0.4 Hz) but not in the low-frequency band (LF; 0.04-0.15 Hz), leading to a significantly elevated LF/HF ratio in the former group. A significant circadian rhythm in LF power and heart rate occurred in both groups, and a significant correlation was found between sleepiness and sympathovagal balance (r = .53, p < .05). These findings indicate not only an autonomic imbalance in the first group compared with controls, but also two strategies of the autonomic nervous system to fight against fatigue in women. One implies circadian control and the other homeostatic control, and both are reflected by the LF/HF ratio.
authors.affiliation: Thermophysiological Chronobiology, Centre for Chronobiology, Psychiatric Hospital of the University of Basel, Basel, Switzerland.
authors.forename: Doreen
authors.initials: D
authors.lastname: Anders
authors.forename: Stephanie
authors.initials: S
authors.lastname: Vollenweider
authors.forename: Judith
authors.initials: J
authors.lastname: Cann
authors.forename: Marcel
authors.initials: M
authors.lastname: Hofstetter
authors.forename: Josef
authors.initials: J
authors.lastname: Flammer
authors.forename: Selim
authors.initials: S
authors.lastname: Orgül
authors.forename: Kurt
authors.initials: K
authors.lastname: Kräuchi
mesh_terms: D001341:Autonomic Nervous System / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D001831:Body Temperature; D002940:Circadian Rhythm / Q000502:physiology; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D012119:Respiration; D014851:Wakefulness