title: Sedentary time and breast cancer incidence in African American women.
abstract: The objective of this study was to evaluate whether time spent sitting at work or watching television was associated with breast cancer risk among African American women.
  
  
  
  The Black Women's Health Study (analytic cohort = 46,734) is an ongoing prospective cohort study of African American women ages 21-69 at baseline (1995). Questionnaire data were used to estimate sedentary time. Total time spent sitting at work and watching television (individually and combined) at baseline and updated through follow-up (1995-2001) and breast cancer incidence (n = 2,041 incident cases, 1995-2013) was evaluated using proportional hazards regression.
  
  
  
  Higher total time spent sitting at baseline (≥10 vs. <5 h/day, HR 1.27, 95 % CI 1.06, 1.53) and updated through follow-up (≥10 vs. <5 h/day, HR 1.38, 95 % CI 1.14, 1.66) was associated with an increased breast cancer risk. Associations were stronger for hormone receptor-negative tumors (≥10 vs. <5 h/day, HR 1.70, 95 % CI 1.12, 2.55) compared to hormone receptor-positive tumors (≥10 vs. <5 h/day, HR 1.16, 95 % CI 0.88, 1.52), but tests for heterogeneity were not statistically significant (p heterogeneity = 0.31). Positive associations between total time spent sitting and breast cancer incidence did not differ by physical activity level or body composition measurements.
  
  
  
  Our findings suggest that high sedentary time may increase risk for breast cancer among African American women.
authors.affiliation: Division of Cancer Prevention and Control, Georgetown-Lombardi Comprehensive Cancer Center, Georgetown University, 1000 New Jersey Ave SE, Washington, DC, 20003, USA. sjo36@georgetown.edu.
authors.forename: Sarah J O
authors.initials: SJ
authors.lastname: Nomura
authors.affiliation: Division of Cancer Prevention and Control, Georgetown-Lombardi Comprehensive Cancer Center, Georgetown University, 1000 New Jersey Ave SE, Washington, DC, 20003, USA.
authors.forename: Chiranjeev
authors.initials: C
authors.lastname: Dash
authors.affiliation: Slone Epidemiology Center at Boston University, 1010 Commonwealth Avenue, 4th Floor, Boston, MA, 02215, USA.
authors.forename: Lynn
authors.initials: L
authors.lastname: Rosenberg
authors.affiliation: Slone Epidemiology Center at Boston University, 1010 Commonwealth Avenue, 4th Floor, Boston, MA, 02215, USA.
authors.forename: Julie
authors.initials: J
authors.lastname: Palmer
authors.affiliation: Division of Cancer Prevention and Control, Georgetown-Lombardi Comprehensive Cancer Center, Georgetown University, 1000 New Jersey Ave SE, Washington, DC, 20003, USA.
authors.forename: Lucile L
authors.initials: LL
authors.lastname: Adams-Campbell
mesh_terms: D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data*; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000208:ethnology*; D015331:Cohort Studies; D015444:Exercise; D005260:Female; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D057185:Sedentary Behavior; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology; D016387:Women's Health
keywords: African American; Breast cancer; Physical activity; Sedentary time