title: Does winter darkness in the Artic protect against cancer? The melatonin hypothesis revisited.
abstract: The melatonin hypothesis states that excess exposure to environmental light may contribute to breast cancer risks via impaired pineal secretion of melatonin. A corollary, not considered previously, is that a net annual increase in oncostatic melatonin would be expected in persons who experience a light deficit during extended winter darkness periods; thus, hormone-dependent cancers should occur less frequently in people who reside north, rather than south, of the Arctic circle. Consistent with our prediction, epidemiological data indicate uniformly low risks for hormone-dependent cancers in the Arctic. The available literature on genetic, reproductive, nutritional, life-style, and environmental risk factors provides no obvious clues to the observed cancer patterns. Moreover, diurnal and 24-hour melatonin concentrations in humans living in Arctic regions were reported as high in November-January, when light intensity is low. Since these observations are consistent with our corollary and the associated prediction, we suggest that research on a melatonin-inhibited carcinogenesis in the low-risk populations of the Arctic should be pursued.
authors.affiliation: Institut und Poliklinik für Arbeits- und Sozialmedizin der Universität zu Köln, Cologne (Lindenthal), Germany. tim.erren@uni-koeln.de
authors.forename: T C
authors.initials: TC
authors.lastname: Erren
authors.forename: C
authors.initials: C
authors.lastname: Piekarski
mesh_terms: D000413:Alaska / Q000453:epidemiology; D001110:Arctic Regions / Q000453:epidemiology; D001943:Breast Neoplasms / Q000453:epidemiology / Q000209:etiology; D002170:Canada / Q000453:epidemiology; D003624:Darkness; D005260:Female; D006116:Greenland / Q000453:epidemiology; D006801:Humans; D008297:Male; D008550:Melatonin / Q000502:physiology*; D008954:Models, Biological; D009376:Neoplasms, Hormone-Dependent / Q000453:epidemiology / Q000209:etiology*; D010051:Ovarian Neoplasms / Q000453:epidemiology / Q000209:etiology; D011471:Prostatic Neoplasms / Q000453:epidemiology / Q000209:etiology; D012621:Seasons; D014594:Uterine Neoplasms / Q000453:epidemiology / Q000209:etiology
chemical_list: D008550:Melatonin