[Shift-workers and night-workers' health consequences: State of art and recommendations].

There are in France several millions of shift-workers and night-workers (20 to 25% of employees). These workers are therefore subject to variations in their working and rest schedules. These regular schedule changes are associated with repeated desynchronization of circadian biological clock. The negative impacts on sleep are insomnia, drowsiness, and reduced sleep time in 24hours. There is also a proven effect on the occurrence of a metabolic syndrome, with a likely effect on obesity, type 2 diabetes, blood pressure and coronary artery disease. There is a likely effect on the occurrence of cancer (including breast cancer). Night working is not recommended for pregnant women because of the risk of miscarriage, prematurity and intrauterine growth retardation.