The misalignment of circadian rhythms of body functions is responsible of the so-called “jet lag” (or “shift-lag” in this case) syndrome, characterized by feelings of fatigue, sleepiness, insomnia, digestive troubles, irritability, poorer mental agility, and reduced performance efficiency; a person recovers in a few days depending on the length and duration of the phase shift imposed, personal characteristics (e.g. age), and coping strate- gies.
It is quite obvious that the perturbation of the sleep/wake cycle has its main effect on sleep, that suffers both in quantity and quality according to the timing of shifts and rest periods, the environmental conditions, and the worker’s characteristics and behaviours.