Abstract
BackgroundEvidence regarding the association of the built environment with physical activity is influencing policy recommendations that advocate changing the built environment to increase population-level physical activity. However, to date there has been no rigorous appraisal of the quality of the evidence on the effects of changing the built environment. The aim of this review was to conduct a thorough quantitative appraisal of the risk of bias present in those natural experiments with the strongest experimental designs for assessing the causal effects of the built environment on physical activity.MethodsEligible studies had to evaluate the effects of changing the built environment on physical activity, include at least one measurement before and one measurement of physical activity after changes in the environment, and have at least one intervention site and non-intervention comparison site. Given the large number of systematic reviews in this area, studies were identified from three exemplar systematic reviews; these were published in the past five years and were selected to provide a range of different built environment interventions. The risk of bias in these studies was analysed using the Cochrane Risk of Bias Assessment Tool: for Non-Randomized Studies of Interventions (ACROBAT-NRSI).ResultsTwelve eligible natural experiments were identified. Risk of bias assessments were conducted for each physical activity outcome from all studies, resulting in a total of fifteen outcomes being analysed. Intervention sites included parks, urban greenways/trails, bicycle lanes, paths, vacant lots, and a senior citizen’s centre. All outcomes had an overall critical (n = 12) or serious (n = 3) risk of bias. Domains with the highest risk of bias were confounding (due to inadequate control sites and poor control of confounding variables), measurement of outcomes, and selection of the reported result.ConclusionsThe present review focused on the strongest natural experiments conducted to date. Given this, the failure of existing studies to adequately control for potential sources of bias highlights the need for more rigorous research to underpin policy recommendations for changing the built environment to increase physical activity. Suggestions are proposed for how future natural experiments in this area can be improved.Electronic supplementary materialThe online version of this article (doi:10.1186/s12966-016-0433-3) contains supplementary material, which is available to authorized users.
Highlights
Evidence regarding the association of the built environment with physical activity is influencing policy recommendations that advocate changing the built environment to increase population-level physical activity
Inclusion criteria Studies were included only if they: (i) were included in one of three existing exemplar systematic reviews [10, 19, 20]; (ii) were natural experiments; that is, evaluated interventions that involved a change to the built environment and researchers did not control intervention allocation; (iii) had physical activity as an outcome, including overall physical activity, walking, cycling, active travel, or pedestrian counts; (iv) had outcomes that were taken before and after environmental change; (v) had at least one control/comparison group; (vi) included adults; and (vii) were published in English
There were a total of 82 studies included in the three exemplar systematic reviews
Summary
Evidence regarding the association of the built environment with physical activity is influencing policy recommendations that advocate changing the built environment to increase population-level physical activity. One aspect of the environment that is increasingly receiving research attention is the built environment, which refers to physical structures of the environment that have been constructed or modified by people [4]. This includes buildings, open spaces, footpaths, cycle lanes, parks, and trails. Unlike individual-level approaches, developing a supportive environment has the potential to achieve the biggest reach for long-term, population-wide improvements in physical activity levels [5], and facilitate behaviour change maintenance [6]. Physical activity interventions that reach large numbers of people over sustained periods of time are often more cost-effective than individual-level interventions [7]
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