title: Reallocating Time to Sleep, Sedentary Time, or Physical Activity: Associations with Waist Circumference and Body Mass Index in Breast Cancer Survivors.
abstract: Moderate-to-vigorous intensity physical activity (MVPA) is inversely associated with waist circumference and body mass index (BMI) among breast cancer survivors. Limited research has focused on behaviors that account for larger portions of the day [sleep, sedentary time, and light-intensity physical activity (LPA)]. We investigated the interdependent associations of self-reported sleep, objectively assessed prolonged and short bouts of sedentary time, total LPA, and total MVPA with waist circumference and BMI.
  
  
  
  A cross-sectional sample of breast cancer survivors (N = 256, mean age = 60 years; mean time since diagnosis = 3 years) wore an Actigraph GT3X+ accelerometer during waking hours for 7 days. Participants completed the Pittsburgh Sleep Quality Index and self-reported their waist circumference, height, and weight. An isotemporal substitution approach was used in linear regression models to explore the associations of reallocating time to sleep, sedentary and active behaviors on waist circumference, and BMI, after adjusting for potential confounders.
  
  
  
  Reallocating 30 minutes to MVPA was significantly associated with lower waist circumference when allocated from sleep (-2.50 cm), prolonged sedentary time (-2.51 cm), or LPA (-2.71 cm). Reallocating 30 minutes of prolonged sedentary time to nonprolonged sedentary time was significantly associated with lower waist circumference (-0.94 cm). Similar results were observed for BMI.
  
  
  
  Reallocating 30 minutes to MVPA was associated with significantly lower waist circumference and BMI, as was reallocating 30 minutes of prolonged sedentary time to 30 minutes of nonprolonged sedentary time.
  
  
  
  Increasing MVPA levels and decreasing time spent in prolonged, unbroken sedentary bouts may be avenues for improving body composition in this population. Cancer Epidemiol Biomarkers Prev; 26(2); 254-60. ©2016 AACR.
authors: School of Public Health, Curtin University, Perth, Western Australia, Australia. terry.boyle@curtin.edu.au.|Cancer Control Research, British Columbia Cancer Agency, Vancouver, British Columbia, Canada.|Centre for Medical Research, The University of Western Australia, Perth, Western Australia, Australia.
authors: Terry
authors: T
authors: Boyle
authors: Faculty of Health Disciplines, Athabasca University, Athabasca, Canada.
authors: Jeff K
authors: JK
authors: Vallance
authors: School of Nutrition and Health Promotion, Arizona State University, Phoenix, Arizona.
authors: Matthew P
authors: MP
authors: Buman
authors: Cancer Epidemiology Centre, Cancer Council Victoria, Melbourne, Victoria, Australia.|School of Population and Global Health, The University of Melbourne, Melbourne, Victoria, Australia.|Physical Activity Laboratory, Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia.
authors: Brigid M
authors: BM
authors: Lynch
mesh_terms: D061725:Accelerometry; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D001943:Breast Neoplasms / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D000073116:Cancer Survivors; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D009367:Neoplasm Staging; D057185:Sedentary Behavior; D057566:Self Report; D012890:Sleep / Q000502:physiology*; D015996:Survival Rate / Q000639:trends; D055105:Waist Circumference; D055815:Young Adult