Research Papers: Gastrointestinal CancerAssociation of physical activity and sitting time with incident colorectal cancer in postmenopausal womenGorczyca, Anna M.a; Eaton, Charles B.b; LaMonte, Michael J.c; Garcia, David O.e; Johnston, Jeanne D.f; He, Kag; Bidulescu, Aureliang; Goodman, Deborahh; Groessl, Eriki; Lane, Dorothyd; Stefanick, Marcia L.j; Newcomb, Pollyk; Mouton, Charlesl; Chomistek, Andrea K.gAuthor Information aDepartment of Internal Medicine, Cardiovascular Research Institute, The University of Kansas Medical Center, Kansas City, Kansas bDepartment of Family Medicine and Epidemiology, Brown University Warren Alpert Medical School and School of Public Health, Providence, Rhode Island cDepartment of Epidemiology and Environmental Health, School of Public Health and Health Professions, University at Buffalo, Buffalo dDepartment of Family, Population and Preventive Medicine, School of Medicine, Stony Brook University, Stony Brook, New York eDepartment of Health Promotion Sciences, The University of Arizona Cancer Center, Tuscan, Arizona fDepartment of Kinesiology gDepartment of Epidemiology and Biostatistics, School of Public Health, Indiana University, Bloomington, Indiana hDepartment of Epidemiology, School of Medicine, University of California Irvine, Irvine iDivision of Behavioral Medicine, Department of Family Medicine and Public Health, School of Medicine, University of California San Diego, San Diego California jDepartment of Medicine, Stanford Prevention Research Center, Stanford University, Stanford, California kDepartment of Cancer Prevention, Fred Hutchinson Cancer Research Center, Seattle, Washington lDepartment of Family and Community Medicine, Meharry Medical College, Nashville, Tennessee, USA Correspondence to Anna M. Gorczyca, PhD, Center for Physical Activity and Weight Management, Department of Internal Medicine, Cardiovascular Research Institute, University of Kansas Medical Center, Kansas City, KS 66160, USA Tel: +9 135 889 077; fax: +9 139 458 280; e-mail: [email protected] European Journal of Cancer Prevention: July 2018 - Volume 27 - Issue 4 - p 331-338 doi: 10.1097/CEJ.0000000000000351 Buy Metrics Abstract Findings from epidemiological studies have found that physical activity (PA) is associated with a lower risk of colorectal cancer (CRC). Recent studies have found an increased CRC risk with higher sitting time (ST); however, many studies did not include PA as a potential confounder. The objective of this project was to investigate the independent and combined associations of ST and PA with the risk of incident CRC, specifically colon and rectal cancer. Participants in the Women’s Health Initiative Observational Study (n=74 870), 50–79 years of age self-reported ST and PA at baseline, years 3 and 6. Incident CRC was the primary outcome; colon and rectal cancers were the secondary outcomes, which were centrally adjudicated. Over a 13-year follow-up period, 1145 incident cases of CRC were documented. A positive age-adjusted association was found between higher ST (≥10 vs. <5 h/day) and CRC (P for trend=0.04) and colon cancer (P for trend=0.05); however, these associations were attenuated and no longer significant in multivariable-adjusted models. Compared with inactive women (≤1.7 MET-h/week), the multivariable risk of CRC in the high PA (>20 MET-h/week) group was 0.81 (95% confidence interval: 0.66–1.00; P for trend 0.04). Compared with inactive women with high ST (≥10 h/day), there was a trend toward reduced multivariable CRC risks with higher PA irrespective of ST level (interaction=0.64). We observed an inverse association between leisure time PA and the risk of CRC, particularly for rectal cancer. There was no association between ST and CRC in multivariable models. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.