title: Too much sitting and all-cause mortality: is there a causal link?
abstract: Sedentary behaviours (time spent sitting, with low energy expenditure) are associated with deleterious health outcomes, including all-cause mortality. Whether this association can be considered causal has yet to be established. Using systematic reviews and primary studies from those reviews, we drew upon Bradford Hill's criteria to consider the likelihood that sedentary behaviour in epidemiological studies is likely to be causally related to all-cause (premature) mortality.
  
  
  
  Searches for systematic reviews on sedentary behaviours and all-cause mortality yielded 386 records which, when judged against eligibility criteria, left eight reviews (addressing 17 primary studies) for analysis. Exposure measures included self-reported total sitting time, TV viewing time, and screen time. Studies included comparisons of a low-sedentary reference group with several higher sedentary categories, or compared the highest versus lowest sedentary behaviour groups. We employed four Bradford Hill criteria: strength of association, consistency, temporality, and dose-response. Evidence supporting causality at the level of each systematic review and primary study was judged using a traffic light system depicting green for causal evidence, amber for mixed or inconclusive evidence, and red for no evidence for causality (either evidence of no effect or no evidence reported).
  
  
  
  The eight systematic reviews showed evidence for consistency (7 green) and temporality (6 green), and some evidence for strength of association (4 green). There was no evidence for a dose-response relationship (5 red). Five reviews were rated green overall. Twelve (67 %) of the primary studies were rated green, with evidence for strength and temporality.
  
  
  
  There is reasonable evidence for a likely causal relationship between sedentary behaviour and all-cause mortality based on the epidemiological criteria of strength of association, consistency of effect, and temporality.
authors.affiliation: Active Living & Public Health, Institute of Sport, Exercise & Active Living (ISEAL), Victoria University, Footscray Park, Melbourne, VIC, 8001, Australia. stuart.biddle@vu.edu.au.|Baker IDI Heart and Diabetes Institute, Melbourne, Australia. stuart.biddle@vu.edu.au.
authors.forename: Stuart J H
authors.initials: SJ
authors.lastname: Biddle
authors.affiliation: Active Living & Public Health, Institute of Sport, Exercise & Active Living (ISEAL), Victoria University, Footscray Park, Melbourne, VIC, 8001, Australia.
authors.forename: Jason A
authors.initials: JA
authors.lastname: Bennie
authors.affiliation: University of Sydney, Sydney, Australia.
authors.forename: Adrian E
authors.initials: AE
authors.lastname: Bauman
authors.affiliation: University of Sydney, Sydney, Australia.
authors.forename: Josephine Y
authors.initials: JY
authors.lastname: Chau
authors.affiliation: Baker IDI Heart and Diabetes Institute, Melbourne, Australia.|University of Queensland, Brisbane, Australia.|Monash University, Melbourne, Australia.|University of Melbourne, Melbourne, Australia.|Deakin University, Melbourne, Australia.|University of Western Australia, Perth, Australia.|The Australian Catholic University, Sydney, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Dunstan
authors.affiliation: Baker IDI Heart and Diabetes Institute, Melbourne, Australia.|Swinburne University of Technology, Melbourne, Australia.
authors.forename: Neville
authors.initials: N
authors.lastname: Owen
authors.affiliation: University of Sydney, Sydney, Australia.|University College London, London, UK.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Stamatakis
authors.affiliation: Active Living & Public Health, Institute of Sport, Exercise & Active Living (ISEAL), Victoria University, Footscray Park, Melbourne, VIC, 8001, Australia.|Baker IDI Heart and Diabetes Institute, Melbourne, Australia.
authors.forename: Jannique G Z
authors.initials: JG
authors.lastname: van Uffelen
mesh_terms: D002423:Cause of Death; D006801:Humans; D061213:Mortality, Premature; D011187:Posture; D012196:Review Literature as Topic; D057185:Sedentary Behavior