Working night shifts leads to sleep and metabolic disorders, and even severe diseases, according to a study published on 22 June by the French Agency for Food, Environmental and Occupational Health and Safety (ANSES).

In close cooperation with their European and U.S. counterparts, French experts reviewed 24 recent epidemiological studies. They came to the conclusion that there is a proven link between night shift work and sleep disorders (particularly drowsiness), as well as a connection to metabolic syndrome (a combination of conditions including obesity, increased blood pressure and lipid disorders). The researchers also believe that night work is likely to increase the risk of developing type 2 diabetes, coronary diseases and, due to the disruption of biological cycles, even breast cancer.

In 2007, shift work was recognised as "probably carcinogenic to humans" by the International Agency for Research on Cancer (IARC).

The 2015 issue of the European survey on working conditions found that 19% of European workers are engaged in night work. It revealed that night shift workers are generally subject to a higher number of physical risks, greater time pressures (work schedules, time constraints, tight deadlines, etc.), and increased tensions with colleagues or the public.