Sedentary time and postmenopausal breast cancer incidence
Menée aux Etats-Unis à partir des données de la cohorte "Women’s Health Initiative Observational Study" incluant 70 233 femmes âgées de 50 à 79 ans entre 1994 et 1998, cette étude évalue l'association entre un comportement sédentaire, le temps passé en position assise et le risque de cancer du sein après la ménopause (4 115 cas jusqu'en septembre 2015)
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. 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. 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. Conclusions : Results from this study do not support an association between sedentary time and breast cancer incidence.