Suppression of men's responses to seasonal changes in day-length by
modern artificial lighting.
Wehr, Thomas A., Holly A. Giesen, Douglas E. Moul, Erick H. Turner,
and Paul J. Schwartz.
Clinical Psychobiology Branch, National Institute of Mental Health,
Bethesda, Maryland 20892-1390
APStracts 2:0068R, 1995.
We recently reported that humans have conserved mechanisms, like those
that exist in other animals, that detect changes in day-length and
make corresponding adjustments in the duration of nocturnal periods
of secretion of melatonin and of other functions. We detected these
responses in individuals who were exposed to artificial
$QUOTdays$QUOT of different durations. The purpose of the present
study was to determine whether men who are exposed to natural and
artificial light in an urban environment at 39 degrees N are still
able to detect and respond to seasonal changes in duration of the
natural photoperiod. We measured profiles of circadian rhythms during
24-hour periods of constant darkness (<1 lux) and found no summer
-winter differences in durations of nocturnal periods of active
secretion of melatonin, rising levels of cortisol, high levels of
thyrotropin (TSH), and low levels of rectal temperature. The results
of this and our previous study suggest that modern men's use of
artificial light suppresses responses to seasonal changes in the
natural photoperiod that might otherwise occur at this latitude.
Received 16 September 1994; accepted in final form 20 February
1995.
APS Manuscript Number R520-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 March 1995.