BRIEF COMMUNICATION Night-Shift Work and Risk of Colorectal Cancer in the Nurses’ Health Study Eva S. Schernhammer, Francine Laden, Frank E. Speizer, Walter C. Willett, David J. Hunter, Ichiro Kawachi, Charles S. Fuchs, Graham A. Colditz Affiliations of authors: E. S. Schernhammer, Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, and Ludwig Boltzmann-Institute for Applied Cancer Research, Kaiser Franz-Josef-Spital, Vienna, Austria; F. Laden, F. E. Speizer, Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, and Department for Environmental Health, Harvard School of Public Health, and Epidemiology Program, Dana-Farber Cancer Institute/Harvard Cancer Center, Boston; W. C. Willett, Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, and Departments of Epidemiology and Nutrition, Harvard School of Public Health; D. J. Hunter, Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, and Department of Epidemiology, Harvard School of Public Health, and Harvard Center for Cancer Prevention, Boston; I. Kawachi, Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, and Department of Health and Social Behavior, Harvard School of Public Health; C. S. Fuchs, Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, and Department of Adult Oncology, Dana-Farber Cancer Institute; G. A. Colditz, Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, and Department of Epidemiology, Harvard School of Public Health, and Harvard Center for Cancer Prevention, and Epidemiology Program, Dana-Farber Cancer Institute/Harvard Cancer Center. Correspondence to: Eva S. Schernhammer, M.D., M.P.H., Channing Laboratory, 181 Longwood Ave., Boston, MA 02115 (e-mail: eva. schernhammer@channing.harvard.edu). ABSTRACT Exposure to light at night suppresses the physiologic production of melatonin, a hormone that has antiproliferative effects on intestinal cancers. Although observational studies have associated night-shift work with an increased risk of breast cancer, the effect of night-shift work on the risk of other cancers is not known. We prospectively examined the relationship between working rotating night shifts and the risk of colorectal cancers among female participants in the Nurses’ Health Study. We documented 602 incident cases of colorectal cancer among 78 586 women who were followed up from 1988 through 1998. Compared with women who never worked rotating night shifts, women who worked 1–14 years or 15 years or more on rotating night shifts had multivariate relative risks of colorectal cancer of 1.00 (95% confidence interval [CI] = 0.84 to 1.19) and 1.35 (95% CI = 1.03 to 1.77), respectively (Ptrend = .04). These data suggest that working a rotating night shift at least three nights per month for 15 or more years may increase the risk of colorectal cancer in women. Journal of the National Cancer Institute, Vol. 95, No. 11, 825-828, June 4, 2003 Remember we are NOT Doctors and have NO medical training. This site is like an Encylopedia - there are many pages, many links on many topics. Support our work with any size DONATION - see left side of any page - for how to donate. You can help raise awareness of CAM.