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Causal pathways linking environmental change with health behaviour change: Natural experimental study of new transport infrastructure and cycling to work.

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Prins, RG 
Heinen, E 
Griffin, SJ 
Ogilvie, DB 


BACKGROUND: Mechanisms linking changes to the environment with changes in physical activity are poorly understood. Insights into mechanisms of interventions can help strengthen causal attribution and improve understanding of divergent response patterns. We examined the causal pathways linking exposure to new transport infrastructure with changes in cycling to work. METHODS: We used baseline (2009) and follow-up (2012) data (N=469) from the Commuting and Health in Cambridge natural experimental study (Cambridge, UK). Exposure to new infrastructure in the form of the Cambridgeshire Guided Busway was defined using residential proximity. Mediators studied were changes in perceptions of the route to work, theory of planned behaviour constructs and self-reported use of the new infrastructure. Outcomes were modelled as an increase, decrease or no change in weekly cycle commuting time. We used regression analyses to identify combinations of mediators forming potential pathways between exposure and outcome. We then tested these pathways in a path model and stratified analyses by baseline level of active commuting. RESULTS: We identified changes in perceptions of the route to work, and use of the cycle path, as potential mediators. Of these potential mediators, only use of the path significantly explained (85%) the effect of the infrastructure in increasing cycling. Path use also explained a decrease in cycling among more active commuters. CONCLUSION: The findings strengthen the causal argument that changing the environment led to changes in health-related behaviour via use of the new infrastructure, but also show how some commuters may have spent less time cycling as a result.



Cycling, Effectiveness, Environment design, Natural experiment, Physical activity, Psychosocial factors, Walking, Adult, Bicycling, Environment Design, Exercise, Female, Health Behavior, Humans, Male, Self Report, Surveys and Questionnaires, Transportation

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Elsevier BV
Medical Research Council (MC_UU_12015/6)
null (unknown)
Medical Research Council (MR/K023187/1)
Economic and Social Research Council (ES/G007462/1)
Wellcome Trust (087636/Z/08/Z)
TCC (None)
Medical Research Council (MC_UP_1001/1)
NIHR Evaluation Trials and Studies Coordinating Centre (09/3001/06)
The Commuting and Health in Cambridge study was developed by David Ogilvie, Simon Griffin, Andy Jones and Roger Mackett and initially funded under the auspices of the Centre for Diet and Activity Research (CEDAR), a UKCRC Public Health Research Centre of Excellence. Funding from the British Heart Foundation, Economic and Social Research Council, Medical Research Council, National Institute for Health Research and the Wellcome Trust, under the auspices of the UK Clinical Research Collaboration, is gratefully acknowledged. The study was subsequently funded by the National Institute for Health Research Public Health Research programme (project number 09/3001/06). RP, SG and DO are supported by the Medical Research Council [Unit Programme number MC_UP_12015/6] and JP is supported by a National Institute for Health Research (NIHR) post-doctoral fellowship (PDF 2012-05-157). The views and opinions expressed herein are those of the authors and do not necessarily reflect those of the NIHR PHR programme or the Department of Health. The funders had no role in study design, data collection and analysis, the decision to publish, or the preparation of the manuscript. We thank all staff from the MRC Epidemiology Unit Functional Group Team, in particular for study coordination and data collection (led by Cheryl Chapman and Fiona Whittle) and data management. We also thank Alice Dalton for computing the proximity measures used in this analysis and Louise Foley for her contribution to preparing the questionnaire data for analysis.