Desynchronization of the oral temperature circadian rhythm and intolerance to shift work.

The present study tested the hypothesis that subjects with a good tolerance to shift work maintain the circadian period tau of their temperature rhythm equal to 24 h, while tau may differ from 24 h when subjects exhibit one or several clinical signs of intolerance. These latter are mainly: persisting sleep disturbance, persisting fatigue, changes in mood and behaviour, and digestive troubles, from gastritis to overt peptic ulcer. These symptoms were used here to classify the subjects studied. Medications, including all types of sleeping pills, are ineffective. As was the case in the present study, some subjects may tolerate shift work for 35 yr, reaching 57 yr of age without complaint, while others, after several months or many years, quite rapidly (within 6 months) develop symptoms of intolerance.