Internal dissociation of the circadian markers of the cortisol
rhythm in night workers.
Weibel, L., K. Spiegel, M. Follenius, J. Ehrhart, G. Brandenberger.
Laboratoire de Physiologie et de Psychologie Environnementales,
CNRS, 21 rue Becquerel, 67087 Strasbourg Cedex
APStracts 2:0229E, 1995.
In order to determine whether the circadian system of night workers is
adapted to a night-active schedule, we submitted 11 night workers and
11 day-active subjects to a 10-min blood sampling procedure during
their usual sleep-wake cycle, permitting a precise determination of
circadian and ultradian cortisol variations. In night workers the
usual shift of 8-hours in the sleep period was associated with a
distortion of the normal 24-hour cortisol rhythm. The acrophase
exhibited a shift of about 6h30, whereas the quiescent period,
abruptly interrupted by a large peak, underwent a shift of only 3h
and lasted for about 5h, as in day-active subjects. Slow-wave sleep
(SWS) and sleep onset occurred during periods of low or decreasing
cortisol secretory rates, whereas awakenings were associated with an
increase in cortisol secretory rates. These results revealed that the
circadian system of night workers only partially adapts to night work
and that adaptation processes rely on an internal dissociation of the
markers of the cortisol pattern, without disturbing the processes
that couple cortisol release and specific sleep stages.
Received 14 July 1995; accepted in final form 8 November 1995.
APS Manuscript Number E332-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 December 95