Mortality from cancer and other causes in German Airline Crew: Results from a third follow-up study using dose registry date, 1960–2014

Abstract

Background Commercial airline crews are one of the occupational groups with the highest exposure to ionizing radiation. The existing German cohort is one of the largest national cohorts set up to examine occupational health risks in cockpit and cabin crew with a focus on studying radiation-associated cancer mortality. The aim of this study was to extend the follow-up period for an additional 10 years and use newly available dose registry data for exposure assessment for the entire cohort including the cabin crew for the first time. Methods The existing closed cohort was followed-up until the end of 2014. Data linkage with the German dose registry was performed for all individuals known to be active as pilots or cabin crew at the end of the previous follow-up (2004). Exposure data were retrieved for the time period 2004–2014. Vital status was assessed via population registries for all inactive cohort members. For deceased individuals, the cause of death was requested from the respective local public health office. Missing cause of death information (n = 223) was imputed proportional to the frequency of known causes in the cohort. A new method was developed to retrospectively estimate cabin crew dose for pre-registry time (1960–2003). External analyses included calculating standardized mortality ratios (SMR and 95% CI) using German population rates as reference. Poisson regression modelling was used to estimate dose–response relationships in internal analyses. Results Among 26,846 cohort members, there were 1592 deaths [518 (32.5%) cancer-related] and 752,434 person-years of observation time at-risk between 1960 and 2014. A total of 510,564 dose records were available for the entire study period for dose-related analyses. Mean annual effective dose per cohort member was 1.99 mSv in 2014. For cockpit and cabin crew the mean cumulative dose was 43.9 mSv (max. 99.7 mSv) and 30.5 mSv (max. 115.9 mSv), respectively. All-cause mortality was significantly reduced in all cohort subgroups (SMR between 0.48 and 0.70). Mortality for all cancers and cancers associated with radiation, respectively, were similarly reduced, with the exception of brain cancers, which were increased both in male cockpit (n = 210, SMR = 2.01, 95% CI: 1.15–3.28) and female cabin crew (n = 14, SMR = 1.26, 95% CI: 0.60–2.36). Malignant melanoma mortality was non- significantly increased in cockpit crew (n = 10, SMR = 1.88, 95% CI: 0.78–3.85). Dose–response analyses indicated no significant increases in mortality rate per 10 mSv in cabin crew. For cockpit crew, the mortality rate for radiation-associated cancers as well as cerebrovascular and cardiovascular diseases significantly decreased with increasing dose. Conclusion The results of this third follow-up study indicate no increased mortality risk for most cancers and other causes in the German airline crew cohort. Using dose registry data allowed for improved exposure assessment for the entire cohort from 2004 onwards and enabled a new approach to retrospectively estimate cabin crew dose for the years before registry data were available. The now established dose registry link may facilitate future follow-ups and improve cohort retention by providing nearly complete exposure assessment and convenient vital status ascertainment.