title: Associations of objectively assessed physical activity and sedentary time with biomarkers of breast cancer risk in postmenopausal women: findings from NHANES (2003-2006).
abstract: Physical activity reduces the risk of postmenopausal breast cancer through multiple inter-related biologic mechanisms; sedentary time may contribute additionally to this risk. We examined cross-sectional associations of objectively assessed physical activity and sedentary time with established biomarkers of breast cancer risk in a population-based sample of postmenopausal women. Accelerometer, anthropometric and laboratory data were available for 1,024 (n = 443 fasting) postmenopausal women in the U.S. National Health and Nutrition Examination Survey 2003-2006. Associations of quartiles of the accelerometer variables (moderate- to vigorous-intensity activity, light-intensity activity and sedentary time per day; average length of active and sedentary bouts) with the continuous biomarkers were assessed using linear regression models. Following adjustment for potential confounders, including sedentary time, moderate- to vigorous-intensity activity had significant (P < 0.05), inverse associations with all biomarker outcomes (body mass index, waist circumference, C-reactive protein, fasting plasma glucose, fasting insulin and homeostasis model assessment of insulin resistance). Light-intensity activity and sedentary time were significantly associated in fully adjusted models with all biomarkers except fasting glucose. Active bout length was associated with a smaller waist circumference and lower C-reactive protein levels, while sedentary bout length was associated with a higher BMI. The associations of objectively assessed moderate- to vigorous-intensity activity with breast cancer biomarkers are consistent with the established beneficial effects of self-reported exercise on breast cancer risk. Our findings further suggest that light-intensity activity may have a protective effect, and that sedentary time may independently contribute to breast cancer risk.
authors.affiliation: Department of Population Health Research, Alberta Health Services, Calgary, T2N 4N2, Canada. brigid.lynch@albertahealthservices.ca
authors.forename: Brigid M
authors.initials: BM
authors.lastname: Lynch
authors.forename: Christine M
authors.initials: CM
authors.lastname: Friedenreich
authors.forename: Elisabeth A H
authors.initials: EA
authors.lastname: Winkler
authors.forename: Geneviève N
authors.initials: GN
authors.lastname: Healy
authors.forename: Jeff K
authors.initials: JK
authors.lastname: Vallance
authors.forename: Elizabeth G
authors.initials: EG
authors.lastname: Eakin
authors.forename: Neville
authors.initials: N
authors.lastname: Owen
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000097:blood / Q000378:metabolism*; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000378:metabolism*; D005260:Female; D006801:Humans; D008875:Middle Aged; D009043:Motor Activity; D009749:Nutrition Surveys; D017698:Postmenopause; D012306:Risk; D057185:Sedentary Behavior
chemical_list: D014408:Biomarkers, Tumor