Naturally, the human body follows a 24-hour sleep-wake cycle, known as the circadian rhythm, regulated by environmental cues such as daylight. Night shifts and irregular working hours have a significant impact on this cycle. These people can accumulate a sleep debt, as it is often more difficult to get enough sleep during the day. This can lead to chronic sleep debt (reduction of 1 to 2 hours sleep per day). The quality of daytime sleep is also poorer: it is often less deep and more fragmented than nocturnal sleep.
Several strategies can be put in place to limit these impacts, such as maintaining a regular sleep schedule even on days off, and creating a dark, quiet and cool environment in which to sleep during the day.

For further information, we recommend that you consult :

- Institut national du Sommeil et de la Vigilance website
- The website of ANSES, the French Agency for Food, Environmental and Occupational Health and Safety (Agence nationale de sécurité sanitaire de l'alimentation, de l'environnement et du travail)
- INRS website