ChronobiologiaJan 1, 1989

Mismatch of body clocks and adapting to shift work

Circadian Biology Weekly Brief ↗PubMed ↗

Updated Apr 2, 2026

Abstract

Intolerance of shift work is frequently associated with internal desynchronization among circadian rhythms.

Continuous recording of temperature and wrist activity, along with grip strength, heart rate, and peak expiratory flow, was conducted.
Analysis revealed individual differences in the circadian period tau, which may relate to tolerance of shift work.
Self-rated drowsiness, fatigue, and attention did not show a similar pattern of internal desynchronization.
The presence of internal desynchronization in tolerant shift workers suggests that symptoms of intolerance may be linked to individual sensitivity rather than the desynchronization itself.
Unequal values of tau in grip strength rhythms indicate potential differences in circadian control mechanisms between the right and left hemispheres.

Simplified

Fifteen male subjects including 12 shift workers (oil refinery operators) volunteered to document circadian rhythms in sleep-wake, grip strength of both hands, peak expiratory flow, heart rate, self-rated drowsiness, fatigue and attention. Each of these variables was measured 4 to 6 times/day for 2 to 3 weeks. In addition, both axillary temperature (with a shielded probe) and wrist activity were almost continuously recorded at 15 min intervals during the same time span. Individual time series were analyzed according to several statistical methods (power spectrum, cosinor, chi 2, etc.), in order to estimate the prominent circadian period tau and to evaluate both individual and subgroup differences with regard to tolerance of shift work, age, duration of shift work. The present study confirms for continuously recorded temperature and wrist activity, grip strength of both hands, heart rate and peak expiratory flow that intolerance of shift work is frequently associated with an internal desynchronization. However, this conclusion cannot be extended to circadian rhythms in self-rated drowsiness, fatigue and attention. The internal desynchronization among several circadian rhythms supports the hypothesis that these latter are driven by several oscillators, with presumable differences between right and left hemispheres as suggested by unequal values of tau in rhythms of both hand grip strength. Since an internal desynchronization can be observed in tolerant shift workers having no complaint, it is likely that symptoms of intolerance are related to the subject's sensitivity to internal desynchronization rather than to the desynchronization itself.

Mismatch of body clocks and adapting to shift work

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