Disruption of the circadian system by environmental factors: Effects of hypoxia, magnetic fields and general anesthetics agents.

The biological clock of mammals is under the control of external factors, social life and the environment, and of internal genetic factors. When the biological clock of an individual is no longer in phase with its environment, either because there is no longer any harmony (desynchronization) between the two systems (shift work, night work, and transmeridian flights...) or because the perception of signals in the environment is defective (blindness) or because of a pathology, disorders of the biological clock occur resulting in persistent fatigue, sleep disorders leading to chronic insomnia and mood disturbances that can cause depression. We review here new groups of factors that have been recently studied and that can be considered as potential disruptors of the circadian time structure. These factors are hypoxia, magnetic fields and anesthetic agents whose importance has to be considered.