Flight attendants, breast cancer, and melatonin

Abstract

The two-fold increased breast cancer risk observed among Finnish female flight attendants was originally suggested to reflect their increased exposure to ionising radiation associated with high-altitude flying.1Pukkala E Auvinen A Wahlberg G Incidence of cancer among Finnish airline cabin attendants, 1967–92.BMJ. 1995; 311: 649-652Crossref PubMed Scopus (211) Google Scholar Another likely explanation, as Anthony Mawson reports,2Mawson AR Breast cancer in female flight attendants.Lancet. 1998; 352: 626Summary Full Text Full Text PDF PubMed Scopus (36) Google Scholar is that such increased risk reflects the lower concentrations of melatonin associated with continued interruptions in normal sleep-waking cycles (jetlag). Accordingly, increased risk of breast cancer should be expected in those attendants with increased work-associated exposure to jetlag. Mawson's alternative interpretation is supported by a study by Tynes and colleagues3Tynes T Hannevik M Andersen A Vistnes AI Haldorsen T Incidence of breast cancer in Norwegian female radio and telegraph operators.Cancer Causes Control. 1996; 7: 197-204Crossref PubMed Scopus (227) Google Scholar on increased risk of breast cancer among Norwegian female radio and telegraph operators. The investigators found a strong association between incidence of breast cancer in women aged older than 50 years and shift work, which continued after adjustment for fertility factors.3Tynes T Hannevik M Andersen A Vistnes AI Haldorsen T Incidence of breast cancer in Norwegian female radio and telegraph operators.Cancer Causes Control. 1996; 7: 197-204Crossref PubMed Scopus (227) Google Scholar Business is increasingly done around the clock, which forces many employees to work rotating shifts, thereby impairing their circadian rhythms.4Van Reeth O Sleep and circadian disturbances in shift work: strategies for their management.Horm Res. 1998; 49: 158-162Crossref PubMed Scopus (28) Google Scholar The medical community should pay more attention to the harmful effects of rotating shift working on immune status and risk of cancer.