title: Cosmic radiation increases the risk of nuclear cataract in airline pilots: a population-based case-control study.
abstract: BACKGROUND
  Aviation involves exposure to ionizing radiation of cosmic origin. The association between lesions of the ocular lens and ionizing radiation is well-known.
  
  
  OBJECTIVE
  To investigate whether employment as a commercial airline pilot and the resulting exposure to cosmic radiation is associated with lens opacification.
  
  
  METHODS
  This is a population-based case-control study of 445 men. Lens opacification was classified into 4 types using the World Health Organization simplified grading system. These 4 types, serving as cases, included 71 persons with nuclear cataracts, 102 with cortical lens opacification, 69 with central optical zone involvement, and 32 with posterior subcapsular lens opacification. Control subjects are those with a different type of lens opacification or without lens opacification. Exposure was assessed based on employment time as pilots, annual number of hours flown on each aircraft type, time tables, flight profiles, and individual cumulative radiation doses (in millisieverts) calculated by a software program. Odds ratios were calculated using logistic regression.
  
  
  RESULTS
  The odds ratio for nuclear cataract risk among cases and controls was 3.02 (95% confidence interval, 1.44-6.35) for pilots compared with nonpilots, adjusted for age, smoking status, and sunbathing habits. The odds ratio for nuclear cataract associated with estimation of cumulative radiation dose (in millisieverts) to the age of 40 years was 1.06 (95% confidence interval, 1.02-1.10), adjusted for age, smoking status, and sunbathing habits.
  
  
  CONCLUSIONS
  The association between the cosmic radiation exposure of pilots and the risk of nuclear cataracts, adjusted for age, smoking status, and sunbathing habits, indicates that cosmic radiation may be a causative factor in nuclear cataracts among commercial airline pilots.
authors.affiliation: Department of Preventive Medicine, University of Iceland, Neshagi 16, 107 Reykjavik, Iceland. vilraf@hi.is
authors.forename: Vilhjalmur
authors.initials: V
authors.lastname: Rafnsson
authors.forename: Eydis
authors.initials: E
authors.lastname: Olafsdottir
authors.forename: Jon
authors.initials: J
authors.lastname: Hrafnkelsson
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sasaki
authors.forename: Arsaell
authors.initials: A
authors.lastname: Arnarsson
authors.forename: Fridbert
authors.initials: F
authors.lastname: Jonasson
mesh_terms: D000337:Aerospace Medicine / Q000706:statistics & numerical data; D000368:Aged; D000401:Aircraft; D016022:Case-Control Studies; D002386:Cataract / Q000453:epidemiology* / Q000209:etiology; D003359:Cosmic Radiation / Q000009:adverse effects*; D006801:Humans; D007055:Iceland / Q000453:epidemiology; D007907:Lens Nucleus, Crystalline / Q000528:radiation effects*; D008297:Male; D008875:Middle Aged; D016273:Occupational Exposure; D016017:Odds Ratio; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000453:epidemiology* / Q000209:etiology; D011839:Radiation, Ionizing; D012307:Risk Factors