INTERINDIVIDUAL DIFFERENCES IN THE FLEXIBILITY OF HUMAN TEMPORAL ORGANIZATION - PERTINENCE TO JET-LAG AND SHIFTWORK

Interindividual variability in the human temporal structure is seldom taken into account, especially in studies devoted to the effects of sh iftwork and jet lag. The understated postulate is that humans can be t reated as a pure strain species. This paper reviews some facts and con cepts with special reference to interindividual changes in the rhythm period tau and the resulting dyschronism. The following points are add ressed. (1) Subjects and methods (importance of longitudinal field stu dies on shift workers). (2) Criteria for tolerance to shiftwork and je t lag. (3) Interindividual differences and shiftwork problems (subject type; the association between good shiftwork tolerance and stable tem poral structure; dychronism with tau s differing from 24h and from var iable to variable. (4) The genetic background Of circadian dyschronism . The Dian-circadian genetic model of biological rhythms. It allows un derstanding of one's susceptibility to dyschronism, which was actually observed in congruent to 30% of subjects studied longitudinally. (5) Practical implications of interindividual differences (dissociate prob lems of passengers after a transmeridian flight-who have to adjust the ir temporal structure to local time-from problems of shiftworkers-who need to prevent alteration of their temporal structure; the advantage for the latter of participating in a rapid rotation system rather than a weekly rotation; emphasis that the suitability of a given subject f or a given shiftworking condition is likely to be estimated only after a trial span of time including longitudinal study of a set of rhythms ).