Citation: Cancer Causes & Control. 28(12):1405-1416, 2017 Dec..Journal: Cancer causes & control : CCC.Published: 2017ISSN: 0957-5243.Full author list: Nomura SJO; Dash C; Sheppard VB; Bowen D; Allison M; Barrington W; Chlebowski R; Coday M; Hou L; Howard B; LaMonte M; Manson JE; Neuhouser ML; Paskett E; Sattari M; Stefanick M; Wactawski-Wende J; Adams-Campbell LL.UI/PMID: 28975422.Subject(s): Aged | *Breast Neoplasms/ep [Epidemiology] | Breast Neoplasms/eh [Ethnology] | Continental Population Groups | Ethnic Groups | Exercise | Female | Humans | Incidence | Middle Aged | *Postmenopause | Proportional Hazards Models | Prospective Studies | *Sedentary Lifestyle | Surveys and QuestionnairesInstitution(s): MedStar Health Research InstituteActivity type: Journal Article.Medline article type(s): Journal ArticleDigital Object Identifier: https://dx.doi.org/10.1007/s10552-017-0968-x (Click here)Abbreviated citation: Cancer Causes Control. 28(12):1405-1416, 2017 Dec.Abstract: PURPOSE: The objective of this study was to evaluate the prospective association between sedentary time and postmenopausal breast cancer incidence, and whether associations differ by race/ethnicity, physical activity levels, and body measurements.Abstract: METHODS: The Women's Health Initiative Observational Study is a prospective cohort among women ages 50-79 years at baseline (1994-1998) (analytic cohort=70,233). Baseline questionnaire data were used to estimate time spent sitting and total sedentary time. Associations between time spent sitting and invasive breast cancer incidence overall (n=4,115 cases through September 2015), and by hormone receptor subtypes, were investigated using Cox proportional hazards regression. Analyses were replicated stratified by race/ethnicity, body measurements, and physical activity.Abstract: RESULTS: Among women in this study, 34.5% reported<=5 h/day sitting, 40.9% reported 6-9 h/day and 24.7% reported>=10 h/day. Time spent sitting (>=10 vs. <=5 h/day adjusted HR=1.00, 95% CI 0.92-1.09) was not associated with breast cancer incidence, regardless of hormone receptor subtype. Associations did not differ by race/ethnicity, physical activity, or body measurements.Abstract: CONCLUSIONS: Results from this study do not support an association between sedentary time and breast cancer incidence.