IS RHYTHM AMPLITUDE RELATED TO ABILITY TO PHASE-SHIFT CIRCADIAN-RHYTHMS OF SHIFT-WORKERS

  • 1 January 1978
    • journal article
    • research article
    • Vol. 74  (4) , 405-409
Abstract
The magnitude of the circadian acrophase adjustment to a phase shift of socio-ecologic synchronizers (as in shift-work) varied from subject to subject. To test the hypothesis that the ability to adjust rapidly to a phase-shift could be associated with having a small amplitude for certain circadian rhythms, the correlation coefficient (r) between the mean circadian rhythm amplitude (A) and the acrophase shift .**GRAPHIC**. measured after the 1st night-shift) were calculated from estimates of chronobiological time series analyses (Halberg''s single cosinor method). Data were obtained from 2 groups of selected shift-workers (20 and 5 subjects, respectively). A negative correlation between A and .**GRAPHIC**. (the smaller the amplitude, the greater the .**GRAPHIC**. was observed in the circadian rhythms of the following variables: oral temperature (r = .63; P < .01), peak expiratory flow (r = .53; P < .01) and urinary 17-OHCS [hydroxycorticosteroids] (r = .60; P < .01), but not for other variables such as grip strength or urinary K+ and Na+. The small amplitude of certain circadian rhythms could be considered as an index of an individual''s ability to phase-shift easily. However, chronobiological characteristics, other than the small circadian rhythm amplitude, remain to be identified, for a better detection of ability to do shift-work and a better knowledge for practical applications.