Shift work and cancer: the evidence and the challenge.
BACKGROUND
In 2007, the International Agency for Research on Cancer (IARC) classified shift work with circadian disruption or chronodisruption as a probable human carcinogen. Short-term disturbances of biological 24-hour-rhythms following exposures to light and darkness at unusual times are well-known as "jet-lag" and "shift-lag" symptoms. However, that chronic disturbances or disruptions of timely sequenced circadian rhythms (chronodisruption) should contribute to long-term developments of cancer is a relatively new concept. This review provides background and practical information with regard to the open question "does shift-work cause cancer?"


METHODS
Overview on the basis of a selective literature search via Medline and ISI Web of Knowledge until 2009 from the viewpoints of occupational medicine, epidemiology, chronobiology, and occupational science.


RESULTS
The postulated causal links between shift-work and cancer in humans are biologically plausible in the light of experimental findings, but to date we lack epidemiological studies which could describe or exonerate risks in humans. Monetary compensation has already been paid for such cases in at least one country (Denmark). In Germany, however, according to the applicable law, a new occupational disease can only be recognized when certain conditions for the recognition of "general scientific merit" have been met. We present the current state of knowledge regarding prevention.


CONCLUSIONS
While causal links between shift-work and cancer developments are not established, future shift-work planning should pay more attention to insights from occupational medicine, chronobiology, and occupational science.
Erren
Thomas C
TC
Institut und Poliklinik für Arbeitsmedizin, Umweltmedizin und Präventionsforschung, Universität zu Köln, Köln, Germany. tim.erren@uni-koeln.de
Falaturi
Puran
P
Morfeld
Peter
P
Knauth
Peter
P
Reiter
Russel J
RJ
Piekarski
Claus
C
D015984:Causality; D002423:Cause of Death; D002940:Circadian Rhythm; D003431:Cross-Cultural Comparison; D003430:Cross-Sectional Studies; D005104:Expert Testimony / Q000331:legislation & jurisprudence; D006801:Humans; D009369:Neoplasms / Q000453:epidemiology / Q000209:etiology* / Q000401:mortality; D009784:Occupational Diseases / Q000453:epidemiology / Q000209:etiology* / Q000401:mortality; D012307:Risk Factors; D020178:Sleep Disorders, Circadian Rhythm / Q000150:complications* / Q000453:epidemiology / Q000401:mortality; D015996:Survival Rate; D014940:Work Schedule Tolerance; D014942:Workers' Compensation / Q000331:legislation & jurisprudence