BACKGROUND: Melatonin shows potential oncostatic activity and is acutely suppressed by light exposure. Some evidence suggests an association between night work and breast cancer risk, possibly through the melatonin pathway. METHODS: In a cohort of premenopausal nurses, we prospectively studied the relation between rotating night shift work and breast cancer risk. Total number of months during which the nurses worked rotating night shifts was first assessed at baseline in 1989 and periodically updated thereafter. We used Cox proportional hazards models to calculate relative risks (RRs) and 95% confidence intervals (CIs). RESULTS: Among 115,022 women without cancer at baseline, 1,352 developed invasive breast cancer during 12 years of follow up. Women who reported more than 20 years of rotating night shift work experienced an elevated relative risk of breast cancer compared with women who did not report any rotating night shift work (multivariate RR = 1.79; 95% CI = 1.06-3.01). There was no increase in risk associated with fewer years of rotating night work. CONCLUSION: Our results suggest a modestly elevated risk of breast cancer after longer periods of rotating night work. Additional studies are warranted to rule out small sample size or uncontrolled sources for confounding as alternative explanations.
BACKGROUND:Melatonin shows potential oncostatic activity and is acutely suppressed by light exposure. Some evidence suggests an association between night work and breast cancer risk, possibly through the melatonin pathway. METHODS: In a cohort of premenopausal nurses, we prospectively studied the relation between rotating night shift work and breast cancer risk. Total number of months during which the nurses worked rotating night shifts was first assessed at baseline in 1989 and periodically updated thereafter. We used Cox proportional hazards models to calculate relative risks (RRs) and 95% confidence intervals (CIs). RESULTS: Among 115,022 women without cancer at baseline, 1,352 developed invasive breast cancer during 12 years of follow up. Women who reported more than 20 years of rotating night shift work experienced an elevated relative risk of breast cancer compared with women who did not report any rotating night shift work (multivariate RR = 1.79; 95% CI = 1.06-3.01). There was no increase in risk associated with fewer years of rotating night work. CONCLUSION: Our results suggest a modestly elevated risk of breast cancer after longer periods of rotating night work. Additional studies are warranted to rule out small sample size or uncontrolled sources for confounding as alternative explanations.
Authors: Qian Li; Tongzhang Zheng; Theodore R Holford; Peter Boyle; Yawei Zhang; Min Dai Journal: Cancer Causes Control Date: 2010-10-07 Impact factor: 2.506
Authors: Lara G Sigurdardottir; Unnur A Valdimarsdottir; Katja Fall; Jennifer R Rider; Steven W Lockley; Eva Schernhammer; Lorelei A Mucci Journal: Cancer Epidemiol Biomarkers Prev Date: 2012-05-07 Impact factor: 4.254
Authors: Kathryn M Emmer; Kathryn L G Russart; William H Walker; Randy J Nelson; A Courtney DeVries Journal: Behav Neurosci Date: 2018-06-28 Impact factor: 1.912
Authors: Ruby Fore; Jaime E Hart; Christine Choirat; Jennifer W Thompson; Kathleen Lynch; Francine Laden; Jorge E Chavarro; Peter James Journal: Cancer Epidemiol Biomarkers Prev Date: 2020-02-25 Impact factor: 4.254