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. Aims: 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. E arlier studies of cancer incidence and cancer mortality among aircrew personnel have shown that overall cancer risk incidence and mortality are comparable with that in the general population.1 However, several studies have found increased breast cancer risk among female cabin crew. [2][3][4][5][6][7][8][9] This has been suggested to reflect occupational exposure to cosmic radiation, hormonal alterations due to repeated jet lag, lifestyle factors, or confounding by factors such as age at menarche and menopause. The contribution of various factors has remained unclear, due to the fact that all earlier reports have limited extent of information on potential confounders-that is, the well known risk factors for breast cancer.We conducted a nested case-control study of breast cancer among cabin attendants in Finland. The purpose of the study was to assess the contribution of occupational versus nonoccupational factors to breast cancer risk among cabin crew. METHODS Data collectionThe source population consisted of all Finnish female airline cabin attendants, who were born in 1960 or before. A total of 1098 eligible woman were identified in the source population from the files of Finnair and Finnish Cabin Crew Union (table 1).In the source populat...

Chronodisruption and cancer

“…We identified 21 individual studies found eligible for metaanalyses of breast and/or prostate cancer in flight personnel (Pukkala et al 1995;Band et al 1996;Lynge 1996;Wartenberg and Stapleton 1998;Gundestrup and Storm 1999;Irvine and Davies 1999;Rafnsson et al 2000;Haldorsen et al 2001;Rafnsson et al 2001;Ballard et al 2002;Blettner et al 2002;Hammar et al 2002;Reynolds et al 2002;Zeeb et al 2002;Linnersjo et al 2003;Paridou et al 2003;Rafnsson et al 2003;Kojo et al 2005) and 9 individual studies with information about breast or prostate cancer risks in shift workers (Tynes et al 1996;Davis et al 2001;Hansen 2001;Schernhammer et al 2001;Kubo et al 2006;Lie et al 2006;O'Leary et al 2006;Schernhammer et al 2006;Conlon et al 2007). Pooled analyses using original data sets from Nordic countries (Pukkala et al 2002 and across Europe Zeeb et al 2003) were not considered in view of a significant overlap with the selected individual studies.…”

“…In fact, except for the standardization of incidence and mortality (for age, calendar period), a classic epidemiological method for the comparison of rates, only two investigations considered possibly relevant covariates of breast Kojo et al 2005) and prostate cancer. Once again, the lack of control of relevant covariates can be explained by the fact that the vast majority of epidemiological investigations was not designed to capture possible breast or prostate cancer risks through CD.…”

Nightshift work and risk of breast cancer and other cancers—a critical review of the epidemiologic evidence

“…Rafnsson et al (83) reported an increasing risk of breast cancer as the length of employment increased among Icelandic cabin attendants flying long-haul international flights in the pre-jet period, but no trend was evident after jet planes were introduced. Kojo et al (68) showed no evidence that the risk of breast cancer increased as the number of long-haul flights increased among Finnish female cabin attendants.…”

Shift work and cancer – considerations on rationale, mechanisms, and epidemiology

“…In case of studies on flight attendants (156)(157)(158)(159)(160)(161)(162)(163)(164)(165)), some of whom tested positive for breast cancer (table 2), many authors claimed the possible concomitant exposure was associated with other risk factors, such as cosmic radiation and jetlag, although no study could report any quantification. This was also the case for the radio and telegraph operators investigated by Tynes et al (8), for whom "shift work highly reflects frequent presence in the radio room both at night and during the day, with possible exposure to light at night, and RF [radio frequency] and ELF [extremely low frequency] fields.…”