Special Section on Cancer and Rhythm Original Paper

Cancer Causes & Control

, Volume 17, Issue 4, pp 489-500

First online:

Biological Clocks and Shift Work: Circadian Dysregulation and Potential Long-term Effects

  • Erhard HausAffiliated withDepartment of Laboratory Medicine & Pathology, University of Minnesota, Health Partners Medical Group, Regions Hospital Email author 
  • , Michael SmolenskyAffiliated withSchool of Public Health, University of Texas – Houston

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Long-term epidemiologic studies on large numbers of night and rotating shift workers have suggested an increase in the incidence of breast and colon cancer in these populations. These studies suffer from poor definition and quantification of the work schedules of the exposed subjects. Against this background, the pathophysiology of phase shift and phase adaptation is reviewed. A phase shift as experienced in night and rotating shift work involves desynchronization at the molecular level in the circadian oscillators in the central nervous tissue and in most peripheral tissues of the body. There is a change in the coordination between oscillators with transient loss of control by the master-oscillator (the Suprachiasmatic Nucleus, SCN) in the hypothalamus. The implications of the pathophysiology of phase shift are discussed for long-term health effects and for the design of ergonomic work schedules minimizing the adverse health effects upon the worker.


Shift work Circadian desynchronization Risk factors Heart disease Cancer Ergonomics