PHASE-SHIFTS OF HUMAN CIRCADIAN-RHYTHMS DUE TO SHIFTS OF ARTIFICIAL ZEITGEBERS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 7  (3) , 303-327
Abstract
In special isolation units, circadian rhythms of human subjects were investigated under the influence of artificial 24 h Zeitgebers, with 6 h advance and 6 h delay shifts of the Zeitgeber simulating time zone shifts. In most cases, the biological rhythms followed the Zeitgeber shifts in the course of several days: in rare cases, advancing Zeitgeber shifts were followed by delaying shifts of the biological rhythms of all variables or partitioning of only some variables. The rhythm of activity was re-entrained after both Zeitgeber shifts within a few days, independent of the shift direction. The rhythm of rectal temperature needed more time for re-entrainment than the activity rhythm; the rate of re-entrainment was consistently higher after advance than after delay shifts (direction asymmetry). Mean value and amplitude of the rectal temperature rhythm were for some days reduced after the advance but not after the delay Zeitgeber shift; among the different subjects, the reduction in amplitude was significantly correlated with the direction asymmetry. The rhythm of psychomotor performance (computation speed) re-entrains in parallel to rectal temperature rhythm; i.e., the performance level was decreased after advance but not after delay shifts. The direction asymmetry in the re-entrainment rates seemed to contradict in flight where this rate was mostly higher after westward than after eastward flights. Differences in the re-entrainment behavior after real and simulated time zone shifts disappeared when the designs were approximated and when identical procedures of analyzing were applied. Significant correlations between the re-entrainment behavior and rhythm parameters measured before the Zeitgeber shifts are of practical importance; this behavior was predictable already before the Zeitgeber was changed in any way: the duration of re-entrainment was correlated with the amplitude and the decrement in performance was correlated with the phase of the rectal temperature rhythm. These practical implications may apply to shift work.

This publication has 2 references indexed in Scilit: