title: Breast cancer risk among Finnish cabin attendants: a nested case-control study.
abstract: BACKGROUND
  Earlier studies have found increased breast cancer risk among female cabin crew. This has been suggested to reflect lifestyle factors (for example, age at first birth), other confounding factors (for example, age at menarche), or occupational factors such as exposure to cosmic radiation and circadian rhythm alterations due to repeated jet lag.
  
  
  OBJECTIVE
  To assess the contribution of occupational versus lifestyle and other factors to breast cancer risk among cabin attendants in Finland.
  
  
  METHODS
  A standardised self-administered questionnaire on demographic, occupational, and lifestyle factors was given to 1041 cabin attendants. A total of 27 breast cancer cases and 517 non-cases completed the questionnaire. Breast cancer diagnoses were confirmed through the Finnish Cancer Registry. Exposure to cosmic radiation was estimated based on self-reported flight history and timetables. A conditional logistic regression model was used for analysis.
  
  
  RESULTS
  In the univariate analysis, family history of breast cancer (OR = 2.67, 95% CI: 1.00 to 7.08) was the strongest determinant of breast cancer. Of occupational exposures, sleep rhythm disruptions (OR = 1.72, 95% CI: 0.70 to 4.27) were positively related and disruption of menstrual cycles (OR = 0.71, 95% CI: 0.26 to 1.96) negatively related to breast cancer. However, both associations were statistically non-significant. Cumulative radiation dose (OR = 0.99, 95% CI: 0.83 to 1.19) showed no effect on breast cancer.
  
  
  CONCLUSIONS
  Results suggest that breast cancer risk among Finnish cabin attendants is related to well established risk factors of breast cancer, such as family history of breast cancer. There was no clear evidence that the three occupational factors studied affected breast cancer risk among Finnish flight attendants.
authors.affiliation: STUK-Radiation and Nuclear Safety Authority, Helsinki, Finland. katja.kojo@uta.fi
authors.forename: K
authors.initials: K
authors.lastname: Kojo
authors.forename: E
authors.initials: E
authors.lastname: Pukkala
authors.forename: A
authors.initials: A
authors.lastname: Auvinen
mesh_terms: D000328:Adult; D000337:Aerospace Medicine; D000368:Aged; D000369:Aged, 80 and over; D000401:Aircraft; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000209:etiology; D016022:Case-Control Studies; D003359:Cosmic Radiation / Q000009:adverse effects; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008019:Life Style; D016015:Logistic Models; D008599:Menstruation Disturbances / Q000150:complications; D008875:Middle Aged; D009784:Occupational Diseases / Q000453:epidemiology* / Q000209:etiology; D016273:Occupational Exposure; D018570:Risk Assessment; D012893:Sleep Wake Disorders / Q000150:complications; D011795:Surveys and Questionnaires; D013997:Time Factors; D014195:Travel