A high rate of breast cancer is present among Finnish female flight attendants after a mean of 13·9 years at work (standard incidence ratio 1·87 [95% CI 1·15–2·23]). The risk is most prominent 15 years after recruitment. 1 Pukkala E Auvinen H Wahlberg G Incidence of cancer among Finnish airline cabin attendants, 1967–1992. BMJ. 1995; 311: 649-652 Crossref PubMed Scopus (211) Google Scholar This increase may be due to melatonin deficiency, resulting from work-associated interruptions in sleep-waking cycles (jetlag). Chronic disturbances in circadian rhythm are thought to lead to many of the health problems reported by shift workers, and because flight attendants commonly work at night and travel across many time zones, they are exposed to chronic interruptions in circadian rhythms. 2 Suvanto S Harma M Ilmarinen J Partinen M Effects of 10 h time zone changes on female flight attendants' circadian rhythms of body temperature, alertness and visual search. Ergonomics. 1993; 36: 613-625 Crossref PubMed Scopus (29) Google Scholar