title: All-cause mortality effects of replacing sedentary time with physical activity and sleeping using an isotemporal substitution model: a prospective study of 201,129 mid-aged and older adults.
abstract: BACKGROUND
  Sedentary behaviour, sleeping, and physical activity are thought to be independently associated with health outcomes but it is unclear whether these associations are due to the direct physiological effects of each behaviour or because, across a finite 24-hour day, engagement in one behavior requires displacement of another. The aim of this study was to examine the replacement effects of sedentary behaviour (total sitting, television/computer screen time combined), sleeping, standing, walking, and moderate-to-vigorous physical activity on all-cause mortality using isotemporal substitution modelling.
  
  
  METHODS
  Longitudinal analysis (4.22 ± 0.9 years follow-up/849,369 person-years) of 201,129 participants of the 45 and Up study aged ≥45 years from New South Wales, Australia.
  
  
  RESULTS
  Seven thousand four hundred and sixty deaths occurred over follow-up. There were beneficial associations for replacing total sitting time with standing (per-hour HR: 95 % CI: 0.95, 0.94-0.96), walking (0.86, 0.81-0.90), moderate-to-vigorous physical activity (0.88, 0.85-0.90), and sleeping in those sleeping ≤ 7 h/day (0.94, 0.90-0.98). Similar associations were noted for replacing screen time. Replacing one hour of walking or moderate-to-vigorous physical activity with any other activity class was associated with an increased mortality risk by 7-18%. Excluding deaths in the first 24 months of the follow up and restricting analyses to those who were healthy at baseline did not materially change the above observations.
  
  
  CONCLUSIONS
  Although replacing sedentary behaviour with walking and moderate-to-vigorous physical activity are associated with the lowest mortality risk, replacements with equal amounts of standing and sleeping (in low sleepers only) are also linked to substantial mortality risk reductions.
authors.affiliation: Charles Perkins Centre, University of Sydney, Sydney, Australia. emmanuel.stamatakis@sydney.edu.au.|Exercise and Sport Sciences, Faculty of Health Sciences, University of Sydney, Sydney, Australia. emmanuel.stamatakis@sydney.edu.au.|UCL-PARG (Physical Activity Research Group), Department of Epidemiology and Public Health, University College London, London, UK. emmanuel.stamatakis@sydney.edu.au.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Stamatakis
authors.affiliation: Prevention Research Collaboration, Sydney School of Public Health, University of Sydney, Sydney, Australia.
authors.forename: Kris
authors.initials: K
authors.lastname: Rogers
authors.affiliation: Graduate School of Public Health, San Diego State University, San Diego, CA, USA.
authors.forename: Ding
authors.initials: D
authors.lastname: Ding
authors.affiliation: National Cancer Institute, Behavioral Research Program, Division of Cancer Control and Population Sciences, Bethesda, MD, USA.
authors.forename: David
authors.initials: D
authors.lastname: Berrigan
authors.affiliation: Charles Perkins Centre, University of Sydney, Sydney, Australia.|Prevention Research Collaboration, Sydney School of Public Health, University of Sydney, Sydney, Australia.
authors.forename: Josephine
authors.initials: J
authors.lastname: Chau
authors.affiliation: UCL-PARG (Physical Activity Research Group), Department of Epidemiology and Public Health, University College London, London, UK.|National Centre for Sport & Exercise Medicine, Loughborough University, Loughborough, UK.
authors.forename: Mark
authors.initials: M
authors.lastname: Hamer
authors.affiliation: Charles Perkins Centre, University of Sydney, Sydney, Australia.|Prevention Research Collaboration, Sydney School of Public Health, University of Sydney, Sydney, Australia.
authors.forename: Adrian
authors.initials: A
authors.lastname: Bauman
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001315:Australia; D003201:Computers / Q000706:statistics & numerical data; D015444:Exercise / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009026:Mortality; D009517:New South Wales / Q000453:epidemiology; D011187:Posture / Q000502:physiology; D011446:Prospective Studies; D012307:Risk Factors; D057185:Sedentary Behavior; D012890:Sleep / Q000502:physiology*; D013690:Television / Q000706:statistics & numerical data; D013997:Time Factors