1 Department of Epidemiology, Medical School, University of Athens, 75 M. Asias St, 115 27, Athens, Greece.
2 Department of Public Health, School of Nursing, University of Athens, 123 Papadiamantopoulou St, 115 27, Athens, Greece.
3 Department of Epidemiology and Medical Statistics, School of Public Health, University of Bielefeld, PO Box 10 01 31, 33501 Bielefeld, Germany.
Correspondence: Prof. Dr Maria Blettner, PO Box 10 01 31, 33501 Bielefeld, Germany. E-mail: blettner{at}uni-bielefeld.de
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Abstract |
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Methods We performed a retrospective cohort study including 843 Olympic Airways cockpit crew and 1835 cabin attendants. Standardized mortality ratios (SMR) were calculated based on death rates of the Greek population. Duration of employment as a proxy for occupational exposure was used to stratify the cohort.
Results For cockpit crew, the overall SMR was 0.7 (n = 65, 95% CI: 0.50.9). The SMR for all cancers was also significantly decreased (n = 17; SMR = 0.6; 95% CI: 0.30.9). Most of this reduction was due to a large deficit in lung cancer deaths (SMR = 0.1; 95% CI: 0.00.5). Slight but non-significant increases were noted for brain and liver cancer. The SMR for cardiovascular death was close to unity. Among female cabin attendants the SMR for all causes was 0.8 (95% CI: 0.41.3). The SMR for all cancers was 0.8 (95% CI: 0.31.7). Mortality from breast cancer was not increased. Among male cabin crew, SMR for all causes was 0.5 (95% CI: 0.30.9). Analyses according to duration of employment showed no pattern.
Conclusions In this first-ever occupational cohort study in Greece, Greek aircrew had a low overall and cancer mortality. Due to the small number of events, the strength of our study is limited. The Greek data will be included in a pooled analysis of European studies.
Accepted 6 November 2002
Airline crew members are occupationally exposed to cosmic ionizing radiation and other specific occupational hazards. A number of studies have focused on estimation of cosmic radiation at altitudes relevant to civil aviation.14 Additionally, a number of epidemiological studies investigated mortality among pilots and cabin crew.57
In all mortality studies so far, the standardized mortality ratios (SMR) for all causes for flying personnel were low, consistent with a healthy worker effect.8 Results for specific tumours show no clear pattern, except a slight increase in breast cancer for female cabin crew in some studies9,10 and increased incidence rate of malignant melanoma among pilots1114 and cabin crew.15
We performed a retrospective cohort study among Greek aircrew personnel to investigate their pattern of mortality and compare it with that of the general population. Our study was the first occupational cohort study ever conducted in Greece and part of an upcoming European collaborative study.
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Material and Methods |
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As data obtained for the years before 1960 were incomplete, the study period was taken as 19601997. The number of expected deaths was calculated based on 5-year-age groups and calendar periods. Cause-specific mortality rates for the population in Greece were obtained from the World Health Organization and the National Statistics Service. Deaths were coded according to the International Classification of Diseases, Ninth Revision (ICD-9) by one of the authors (AP) and then cross-checked with the National Statistics Office in Athens.
We calculated SMR for all causes and for specific causes of death. Exact limits for the 95% CI were calculated assuming a Poisson distribution for the observed deaths. All statistical analyses were done using SAS 6.12 software (SAS, Cary, North Carolina).
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Results |
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Tables 12
show observed and expected deaths and resulting SMR with 95% CI for pilots and cabin crew, respectively. The Tables include only causes of death with at least one observed death. Among cockpit crew the SMR for all causes was 0.7 (95% CI: 0.50.9); similarly, for all cancer, SMR was reduced to 0.6 (95% CI: 0.30.9). Lung cancer showed reduced SMR; only one death was observed. The cardiovascular SMR was close to unity (SMR = 1.0; 95% CI: 0.61.5). Nine deaths were due to aircraft accidents; the number of expected deaths is far below 1.00 and so the SMR is high. In the female cabin crew, 6 deaths were due to cancer (SMR = 0.8; 95% CI: 0.31.7). Observed and expected numbers of breast cancer deaths did not differ. The male cabin crew also had a low all-cause and all-cancer mortality compared with the general population. A slightly increased SMR was seen for motor vehicle accidents.
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Discussion |
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The decreased mortality from all causes reflects the healthy worker effect. This phenomenon has been reported by most of the published mortality studies among pilots and cabin crew.5,8
The mortality from lung cancer among pilots in Greece was lower than the general population. Smoking habits were recorded by questionnaires for employees who contacted the Social Security Foundation of the Civil Aviation for health problems. According to these data, approximately 40% were smokers versus 45% in the general population. It is likely that this figure overestimates the smoking prevalence as it is based on people with health problems, and so it can be assumed that smoking is less prevalent in our cohort than in the general population. In contrast to other mortality studies,5 no decrease was observed for mortality from cardiovascular diseases. Probably it is related to nutritional habits different from the traditional Mediterranean diet of the general population. The high number of deaths from aircraft accidents noted in this study is comparable to previously reported observations.
The mortality for all causes and all cancers among cabin crew members was decreased, although based on small numbers of cases. Mortality from breast cancer was equal to the expected. Other studies9,10 reported an increase in incidence of breast cancer.
Data were obtained from several reliable sources, with acceptable completeness and with a 20-year mean duration of follow-up, which contributed to the strength of the study.
A longer follow-up of our study and an ongoing-pooled analysis of our and other cohort studies among flying personnel will be informative in the future.
KEY MESSAGES
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Acknowledgments |
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References |
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