title: Systematic review and meta-analysis of reduction in all-cause mortality from walking and cycling and shape of dose response relationship.
abstract: OBJECTIVE
  Walking and cycling have shown beneficial effects on population risk of all-cause mortality (ACM). This paper aims to review the evidence and quantify these effects, adjusted for other physical activity (PA).
  
  
  METHODS
  We conducted a systematic review to identify relevant studies. Searches were conducted in November 2013 using the following health databases of publications: Embase (OvidSP); Medline (OvidSP); Web of Knowledge; CINAHL; SCOPUS; SPORTDiscus. We also searched reference lists of relevant texts and reviews.
  
  
  METHODS
  Eligible studies were prospective cohort design and reporting walking or cycling exposure and mortality as an outcome. Only cohorts of individuals healthy at baseline were considered eligible.
  
  
  METHODS
  Extracted data included study population and location, sample size, population characteristics (age and sex), follow-up in years, walking or cycling exposure, mortality outcome, and adjustment for other co-variables. We used random-effects meta-analyses to investigate the beneficial effects of regular walking and cycling.
  
  
  RESULTS
  Walking (18 results from 14 studies) and cycling (8 results from 7 studies) were shown to reduce the risk of all-cause mortality, adjusted for other PA. For a standardised dose of 11.25 MET.hours per week (or 675 MET.minutes per week), the reduction in risk for ACM was 11% (95% CI = 4 to 17%) for walking and 10% (95% CI = 6 to 13%) for cycling. The estimates for walking are based on 280,000 participants and 2.6 million person-years and for cycling they are based on 187,000 individuals and 2.1 million person-years. The shape of the dose-response relationship was modelled through meta-analysis of pooled relative risks within three exposure intervals. The dose-response analysis showed that walking or cycling had the greatest effect on risk for ACM in the first (lowest) exposure interval.
  
  
  CONCLUSIONS
  The analysis shows that walking and cycling have population-level health benefits even after adjustment for other PA. Public health approaches would have the biggest impact if they are able to increase walking and cycling levels in the groups that have the lowest levels of these activities.
  
  
  BACKGROUND
  The review protocol was registered with PROSPERO (International database of prospectively registered systematic reviews in health and social care) PROSPERO 2013: CRD42013004266.
authors.affiliation: Nuffield Department of Population Health, British Heart Foundation Centre on Population Approaches for Non-Communicable Disease Prevention, WHO Collaborating Centre on Population Approaches to Non-Communicable Disease Prevention, University of Oxford, Oxford, OX3 7LF, UK. paul.kelly@dph.ox.ac.uk.|Physical Activity for Health Research Centre, Institute for Sport, Physical Education and Health Sciences, University of Edinburgh, Edinburgh, UK. paul.kelly@dph.ox.ac.uk.
authors.forename: Paul
authors.initials: P
authors.lastname: Kelly
authors.affiliation: Institute of Social and Preventive Medicine, Physical Activity and Health, University of Zurich, CH-8001, Zurich, Switzerland. sonja.kahlmeier@ifspm.uzh.ch.
authors.forename: Sonja
authors.initials: S
authors.lastname: Kahlmeier
authors.affiliation: Institute of Social and Preventive Medicine, Physical Activity and Health, University of Zurich, CH-8001, Zurich, Switzerland. thomas.goetschi@ifspm.uzh.ch.
authors.forename: Thomas
authors.initials: T
authors.lastname: Götschi
authors.affiliation: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden. nicola.orsini@ki.se.
authors.forename: Nicola
authors.initials: N
authors.lastname: Orsini
authors.affiliation: Sydney Medical School & Sydney School of Public Health, Charles Perkins Centre, The University of Sydney, Sydney, NSW 2006, Australia. justin.richards@sydney.edu.au.
authors.forename: Justin
authors.initials: J
authors.lastname: Richards
authors.affiliation: Bodleian Health Care Libraries, University of Oxford, Oxford, UK. nia.roberts@bodleian.ox.ac.uk.
authors.forename: Nia
authors.initials: N
authors.lastname: Roberts
authors.affiliation: Nuffield Department of Population Health, British Heart Foundation Centre on Population Approaches for Non-Communicable Disease Prevention, WHO Collaborating Centre on Population Approaches to Non-Communicable Disease Prevention, University of Oxford, Oxford, OX3 7LF, UK. peter.scarborough@dph.ox.ac.uk.
authors.forename: Peter
authors.initials: P
authors.lastname: Scarborough
authors.affiliation: Nuffield Department of Population Health, British Heart Foundation Centre on Population Approaches for Non-Communicable Disease Prevention, WHO Collaborating Centre on Population Approaches to Non-Communicable Disease Prevention, University of Oxford, Oxford, OX3 7LF, UK. charlie.foster@dph.ox.ac.uk.
authors.forename: Charlie
authors.initials: C
authors.lastname: Foster
mesh_terms: D001642:Bicycling; D016208:Databases, Factual; D006304:Health Status; D006801:Humans; D009026:Mortality; D009043:Motor Activity; D011634:Public Health; D012307:Risk Factors; D016138:Walking