Night-Shift Work and Breast Cancer Risk in a Cohort of Chinese Women

Abstract

Shift work involving disruption of circadian rhythms has been classified as a probable cause of human cancer by the International Agency for Research on Cancer, based on limited epidemiologic evidence and abundant experimental evidence. The authors investigated this association in a population-based prospective cohort study of Chinese women. At baseline (1996-2000), information on lifetime occupational history was obtained from 73,049 women. Lifetime night-shift exposure indices were created using a job exposure matrix. During 2002-2004, self-reported data on frequency and duration of night-shift work were collected. Hazard ratios and 95% confidence intervals, adjusted for major breast cancer risk factors, were calculated. During follow-up through 2007, 717 incident cases of breast cancer were diagnosed. Breast cancer risk was not associated with ever working the night shift on the basis of the job exposure matrix (adjusted hazard ratio = 1.0, 95% confidence interval: 0.9, 1.2) or self-reported history of night-shift work (adjusted hazard ratio = 0.9, 95% confidence interval: 0.7, 1.1). Risk was also not associated with frequency, duration, or cumulative amount of night-shift work. There were no indications of effect modification. The lack of an association between night-shift work and breast cancer adds to the inconsistent epidemiologic evidence. It may be premature to consider shift work a cause of cancer.

Emerging functional roles of nuclear receptors in breast cancer

“…Although a few studies reported no significant association between breast cancer and night work (O'Leary et al 2006, Pronk et al 2010, the majority of recent studies reported significant or borderline associations, with the strongest association found with long-term exposure to night work (Hansen 2001, Schernhammer et al 2001, Hansen & Lassen 2012, Hansen & Stevens 2012, Knutsson et al 2013, Menegaux et al 2013, Rabstein et al 2013, Akerstedt et al 2015, Papantoniou et al 2015. Meta-analysis studies have also reported a positive association between night work and breast cancer risk (Jia et al 2013) and that a positive dose-response gradient is observed for breast cancer with increased years of night shift and cumulative night work .…”

Arbeit zur falschen Zeit am falschen Platz? Eine Matching-Analyse zu gesundheitlichen Beanspruchungen bei Schicht- und Nachtarbeit

“…Für Brustkrebsrisiken von Krankenschwestern liegen etwas besser kontrollierte Studien vor (Schernhammer et al 2006). Doch auch hier werden signifikante kausale Zusammenhänge bestritten (Kolstad et al 2010;Pesch et al 2010;Pronk et al 2010). Da Krebserkrankungen im vorliegenden Datensatz nicht enthalten sind und darüber hinaus Langfristfolgen nicht untersucht werden können, müssen sie in dieser Untersuchung unberück-sichtigt bleiben.…”

Night shift work characteristics and occupational co-exposures in industrial plants in Łódź, Poland

“…This database contains a continuously updated set of information on the subjects of national economy, with the activities of the enterprises encoded according to the Polish Classification of Activities (Polska Klasyfikacja Działalności -PKD) further studies was expressed as follows: "more studies are needed to examine this potential risk in other professions and for other cancers" (Dr Cogliano, Head of the IARC Monographs Programme) [2,3]. Over the past 5 years, eight additional epidemiological studies have been reported, including: three investigations in nurses: a Norwegian nested case-control study on breast cancer [4], a Danish nested case-control study on breast cancer [5], an ovarian cancer in Nurses Health Study [6], as well as a breast cancer case-control study in Germany [7], and France -breast cancer case-control CECILE study [8], industrial males cohort in Japan -a study on prostate cancer [9], and females in China -a study on breast cancer [10]. Moreover, one registry-based linkage study was conducted in Scandinavian countries [11].…”