[Chronobiologic features in a 12-hour working day].

A review of investigations into the effects of 12-hour workdays indicates that the extended workday is frequently related to decrement of performance efficiency, alertness and safety, and to increased subjective fatigue during work. Fatigue is increased even more during night shift work. As sleep duration after the night shift is also reduced, combined effects of fatigue and sleep debt can increase the risk of accidents, especially when workers work more nights in a row. In spite of the increased feeling of fatigue the workers prefer longer working hours to an eight-hour working schedule, because they have more free time to use for restitution, leisure and other domestic and second job activities.