Impact of changes in mode of travel to work on changes in body mass index: evidence from the British Household Panel Survey

BACKGROUND Active commuting is associated with various health benefits, but little is known about its causal relationship with body mass index (BMI). METHODS We used cohort data from three consecutive annual waves of the British Household Panel Survey, a longitudinal study of nationally representative households, in 2004/05 (n=15,791), 2005/06 and 2006/07. Participants selected for the analyses (n=4,056) reported their usual main mode of travel to work at each time point. Self-reported height and weight were used to derive BMI at baseline and after two years. Multivariable linear regression analyses were used to assess associations between switching to and from active modes of travel (over one and two years) and change in BMI (over two years) and to assess dose-response relationships. RESULTS After adjustment for socioeconomic and health-related covariates, the first analysis (n=3,269) showed that switching from private motor transport to active travel or public transport (n=179) was associated with a significant reduction in BMI compared to continued private motor vehicle use (n=3,090) (-0.32kg/m2, 95% CI: -0.60 to -0.05). Larger adjusted effect sizes were associated with switching to active travel (n=109) (-0.45kg/m2, -0.78 to -0.11), particularly among those who switched within the first year and those with the longest journeys. The second analysis (n=787) showed that switching from active travel or public transport to private motor transport was associated with a significant increase in BMI (0.34kg/m2, 0.05 to 0.64). CONCLUSION Interventions to enable commuters to switch from private motor transport to more active modes of travel could contribute to reducing population mean BMI

Synthesising evidence for equity impacts of population-based physical activity interventions: a pilot study.

BACKGROUND: This study applied an equity lens to existing research to investigate what is known about the impact of population-level physical activity interventions on social inequalities. METHODS: We performed a pilot systematic review to assess the availability of information on the social distribution of intervention effects, the targeting or allocation of interventions, and the baseline characteristics of participants. This comprised (i) a rapid review of systematic reviews and (ii) a review and synthesis of a sample of primary studies included in the eligible systematic reviews. RESULTS: We found 19 systematic reviews of environmental and policy interventions. Relatively few of these (26%, n=5) were prospectively designed to examine effects on inequalities, and none were able to fully synthesise evidence of distributional effects. Over 40% of primary studies reported subgroup intervention effects; 18% reported socio-demographic interaction effects. Studies most often compared effectiveness by gender, followed by age, ethnicity, and socio-economic status. For gender, effects appeared to be evenly distributed overall, although heterogeneity in gradients between studies suggested that some interventions affect males and females differently. CONCLUSIONS: Our findings suggest that it is feasible to generate better evidence about how public health interventions may affect health inequalities using existing data and innovative methods of research synthesis.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Shifting towards healthier transport? From systematic review to primary research

Promoting a shift from using cars towards walking and cycling (a modal shift) has the potential to improve population health by reducing the adverse health effects associated with exposure to motor traffic and increasing the population level of physical activity through active travel. However, little is known about the effects of interventions which might achieve this by changing urban design, transport infrastructure or other putative determinants of population travel behaviour. I conducted a systematic review of the best available evidence about the effects of interventions to promote a modal shift. I searched twenty electronic literature databases as well as websites, bibliographies and reference lists and invited experts to contribute additional references. I identified 69 relevant studies and devised a two-dimensional hierarchy of study utility based on study design and study population with which I selected a subset of studies for inclusion. I appraised the quality of these studies; extracted data on the effects of interventions on choice of mode of transport, how these effects were distributed in the population, and associated effects on measures of individual and population health and wellbeing; and produced a narrative synthesis of the findings. Twenty-two studies were included. These comprised three randomised controlled trials, seven non-randomised controlled prospective studies, 11 uncontrolled prospective studies, and one controlled retrospective study of interventions applied to urban populations or areas in which outcomes were assessed in a sample of local people. I found some evidence that targeted behaviour change programmes could change the behaviour of motivated subgroups, resulting (in the largest study) in a modal shift of around 5% of all trips at a population level. Single studies of commuter subsidies and a new railway station also showed positive effects. The balance of best available evidence about other types of intervention such as publicity campaigns, traffic calming and cycling infrastructure suggested that they had not been effective. Participants in trials of active commuting experienced short term improvements in certain measures of health and fitness, but I found no good evidence about health effects associated with any effective intervention at population level. Most relevant studies were not found in mainstream health or social science literature databases. Further analysis of the 47 excluded studies did not change the overall conclusions about effectiveness, but did identify additional categories of intervention that merit further research and provided evidence to challenge assumptions about the actual effects of progressive urban transport policies. The contributions of internet publications, serendipitous discoveries and the initially-excluded studies to the total set of relevant evidence suggested that undertaking a comprehensive search may have provided unique evidence and insights that would not have been obtained using a more focused search. I identified an evaluative bias whereby the effects of population-level interventions were less likely than those of individual-level interventions to have been studied using the most rigorous study designs. Understanding of how environmental and policy factors may influence active travel and physical activity currently relies heavily on evidence from cross-sectional studies of correlates rather than intervention studies. I therefore took advantage of the opportunity presented by a local ‘natural experiment’ — the construction of a new urban section of the M74 motorway in Glasgow — to design, develop and complete the cross-sectional (baseline) phase of a new primary study of the effects of a major environmental intervention. Using a combination of census data, geographical data and field visits, I delineated an intervention study area close to the proposed route of the new motorway and two matched control areas elsewhere in Glasgow. I collected and described data from residents in the three study areas (n=1322) on socioeconomic status, the local environment, travel behaviour, physical activity and general health and wellbeing using a postal questionnaire incorporating two established instruments (the SF-8 and the short-form International Physical Activity Questionnaire), a travel diary and a new 14-item neighbourhood rating scale whose test–retest reliability I established in a subset of respondents (n=125). I then analysed the correlates of active travel and physical activity using logistic regression. Using travel diary data from Scottish Household Survey respondents (n=39067), I also compared the characteristics and travel behaviour of residents living close to the proposed route with those living in the rest of Scotland and analysed the correlates of active travel using logistic regression. Overall data quality and the test–retest reliability of the new neighbourhood scale appeared acceptable. Local residents reported less car travel than expected from national data. In the local study area, active travel was associated with being younger, being an owner-occupier, not having to travel a long distance to work and not having access to a car, whereas overall physical activity was associated with living in social-rented accommodation and not being overweight. After adjusting for individual and household characteristics, neither perceptions of the local environment nor the objective proximity of respondents’ homes to motorway or major road infrastructure appeared to explain much of the variance in active travel or overall physical activity, although I did find a significant positive association between active travel and perceived proximity to shops. Apart from access to local amenities, therefore, environmental characteristics may be of limited relevance as explanatory factors for active travel in this comparatively deprived urban population which has a low level of car ownership and may therefore have less capacity for making discretionary travel choices than the populations studied in most published research on the environmental correlates of physical activity. The design and baseline data for the M74 study now provide the basis for a controlled longitudinal study, which could not otherwise have been carried out, of changes in perceptions of the local environment, active travel, physical activity, and general health and wellbeing associated with a major intervention in the built environment. This will, in time, contribute to addressing calls to produce better evidence about the health impacts of natural experiments in public policy

Effects of living near a new urban motorway on the travel behaviour of local residents in deprived areas: Evidence from a natural experimental study

We evaluated the effects of a new motorway built through deprived neighbourhoods on travel behaviour in residents. This natural experiment comprised a longitudinal cohort (n=365) and two cross-sectional samples (baseline n=980; follow-up n=978) recruited in 2005 and 2013. Adults from one of three study areas - surrounding the new motorway (South), an existing motorway (East), or no motorway (North) - completed a previous day travel record. Adjusted two-part regression models examined associations between exposure and outcome. Compared to the North, cohort participants in the South were more likely to undertake travel by any mode (OR 2.1, 95% CI 1.0–4.2) at follow-up. Within the South study area, cohort participants living closer to a motorway junction were more likely to travel by any mode at follow-up (OR 4.7, 95% CI 1.1–19.7), and cross-sectional participants living closer were more likely to use a car at follow-up (OR 3.4, 95% CI 1.1–10.7), compared to those living further away. Overall, the new motorway appeared to promote travel and car use in those living nearby, but did not influence active travel. This may propagate socioeconomic inequalities in non-car owners

Change in active travel and changes in recreational and total physical activity in adults: longitudinal findings from the iConnect study.

BACKGROUND: To better understand the health benefits of promoting active travel, it is important to understand the relationship between a change in active travel and changes in recreational and total physical activity. METHODS: These analyses, carried out in April 2012, use longitudinal data from 1628 adult respondents (mean age 54 years; 47% male) in the UK-based iConnect study. Travel and recreational physical activity were measured using detailed seven-day recall instruments. Adjusted linear regression models were fitted with change in active travel defined as 'decreased' (15 min/week) as the primary exposure variable and changes in (a) recreational and (b) total physical activity (min/week) as the primary outcome variables. RESULTS: Active travel increased in 32% (n=529), was maintained in 33% (n=534) and decreased in 35% (n=565) of respondents. Recreational physical activity decreased in all groups but this decrease was not greater in those whose active travel increased. Conversely, changes in active travel were associated with commensurate changes in total physical activity. Compared with those whose active travel remained unchanged, total physical activity decreased by 176.9 min/week in those whose active travel had decreased (adjusted regression coefficient -154.9, 95% CI -195.3 to -114.5) and was 112.2 min/week greater among those whose active travel had increased (adjusted regression coefficient 135.1, 95% CI 94.3 to 175.9). CONCLUSION: An increase in active travel was associated with a commensurate increase in total physical activity and not a decrease in recreational physical activity

Cycling and Diabetes Prevention: Practice-Based Evidence for Public Health Action.

Panter and Ogilvie describe findings that link recreational and commuter cycling with reduced incidence of diabetes

Motivations for active commuting: a qualitative investigation of the period of home or work relocation.

BACKGROUND: Promoting walking or cycling to work (active commuting) could help to increase population physical activity levels. According to the habit discontinuity and residential self-selection hypotheses, moving home or workplace is a period when people (re)assess, and may be more likely to change, their travel behavior. Research in this area is dominated by the use of quantitative research methods, but qualitative approaches can provide in-depth insight into the experiences and processes of travel behavior change. This qualitative study aimed to explore experiences and motivations regarding travel behavior around the period of relocation, in an effort to understand how active commuting might be promoted more effectively. METHODS: Participants were recruited from the Commuting and Health in Cambridge study cohort in the UK. Commuters who had moved home, workplace or both between 2009 and 2010 were identified, and a purposive sample was invited to participate in semi-structured interviews regarding their experiences of, and travel behavior before and after, relocating. A grounded theory approach was taken to analysis. RESULTS: Twenty-six commuters participated. Participants were motivated by convenience, speed, cost and reliability when selecting modes of travel for commuting. Physical activity was not a primary motivation, but incidental increases in physical activity were described and valued in association with active commuting, the use of public transport and the use of park-and-ride facilities. CONCLUSIONS: Emphasizing and improving the relative convenience, cost, speed and reliability of active commuting may be a more promising approach to promoting its uptake than emphasizing the health benefits, at least around the time of relocation. Providing good quality public transport and free car parking within walking or cycling distance of major employment sites may encourage the inclusion of active travel in the journey to work, particularly for people who live too far from work to walk or cycle the entire journey. Contrary to a straightforward interpretation of the self-selection hypothesis, people do not necessarily decide how they prefer to travel, relocate, and then travel in their expected way; rather, there is constant negotiation, reassessment and adjustment of travel behavior following relocation which may offer an extended window of opportunity for travel behavior change.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Evaluating causal relationships between urban built environment characteristics and obesity: a methodological review of observational studies.

BACKGROUND: Existing reviews identify numerous studies of the relationship between urban built environment characteristics and obesity. These reviews do not generally distinguish between cross-sectional observational studies using single equation analytical techniques and other studies that may support more robust causal inferences. More advanced analytical techniques, including the use of instrumental variables and regression discontinuity designs, can help mitigate biases that arise from differences in observable and unobservable characteristics between intervention and control groups, and may represent a realistic alternative to scarcely-used randomised experiments. This review sought first to identify, and second to compare the results of analyses from, studies using more advanced analytical techniques or study designs. METHODS: In March 2013, studies of the relationship between urban built environment characteristics and obesity were identified that incorporated (i) more advanced analytical techniques specified in recent UK Medical Research Council guidance on evaluating natural experiments, or (ii) other relevant methodological approaches including randomised experiments, structural equation modelling or fixed effects panel data analysis. RESULTS: Two randomised experimental studies and twelve observational studies were identified. Within-study comparisons of results, where authors had undertaken at least two analyses using different techniques, indicated that effect sizes were often critically affected by the method employed, and did not support the commonly held view that cross-sectional, single equation analyses systematically overestimate the strength of association. CONCLUSIONS: Overall, the use of more advanced methods of analysis does not appear necessarily to undermine the observed strength of association between urban built environment characteristics and obesity when compared to more commonly-used cross-sectional, single equation analyses. Given observed differences in the results of studies using different techniques, further consideration should be given to how evidence gathered from studies using different analytical approaches is appraised, compared and aggregated in evidence synthesis.The work was undertaken by the Centre for Diet and Activity Research (CEDAR), a UKCRC Public Health Research Centre of Excellence. Funding from the British Heart Foundation, Cancer Research UK, Economic and Social Research Council (MRC), Medical Research Council, the National Institute for Health Research, and the Wellcome Trust, under the auspices of the UK Clinical Research Collaboration, is gratefully acknowledged. David Ogilvie is also supported by the MRC [Unit Programme number MC_UU_12015/6].This is the final published version. It originally appeared at http://www.ijbnpa.org/content/11/1/142/abstract

Negotiating multisectoral evidence: a qualitative study of knowledge exchange at the intersection of transport and public health.

BACKGROUND: For the prevention and control of chronic diseases, two strategies are frequently highlighted: that public health should be evidence based, and that it should develop a multisectoral approach. At the end of a natural experimental study of the health impacts of new transport infrastructure, we took the opportunity of a knowledge exchange forum to explore how stakeholders assessed, negotiated and intended to apply multisectoral evidence in policy and practice at the intersection of transport and health. We aimed to better understand the challenges they faced in knowledge exchange, as well as their everyday experiences with working in multisectoral remits. METHODS: In 2015, we conducted participant observation during an interactive event with 41 stakeholders from national and local government, the third sector and academia in Cambridge, UK. Formal and informal interactions between stakeholders were recorded in observational field notes. We also conducted 18 semistructured interviews reflecting on the event and on knowledge exchange in general. RESULTS: We found that stakeholders negotiated a variety of challenges. First, stakeholders had to negotiate relatively new formal and informal multisectoral remits; and how to reconcile the differing expectations of transport specialists, who tended to emphasise the importance of precedence in guiding action, and health specialists' concern for the rigour and synthesis of research evidence. Second, research in this field involved complex study designs, and often produced evidence with uncertain transferability to other settings. Third, health outcomes of transport schemes had political traction and were used strategically but not easily translated into cost-benefit ratios. Finally, knowledge exchange meant multiple directions of influence. Stakeholders were concerned that researchers did not always have skills to translate their findings into understandable evidence, and some stakeholders would welcome opportunities to influence research agendas. CONCLUSIONS: This case study of stakeholders' experiences indicates that multisectoral research, practice and policymaking requires the ability and capacity to locate, understand and communicate complex evidence from a variety of disciplines, and integrate different types of evidence into clear business cases beyond sectoral boundaries

Walking and cycling to work despite reporting an unsupportive environment: insights from a mixed-method exploration of counterintuitive findings.

BACKGROUND: Perceptions of the environment appear to be associated with walking and cycling. We investigated the reasons for walking and cycling to or from work despite reporting an unsupportive route environment in a sample of commuters. METHODS: This mixed-method analysis used data collected as part of the Commuting and Health in Cambridge study. 1164 participants completed questionnaires which assessed the travel modes used and time spent on the commute and the perceived environmental conditions on the route to work. A subset of 50 also completed qualitative interviews in which they discussed their experiences of commuting. Participants were included in this analysis if they reported unsupportive conditions for walking or cycling on their route (e.g. heavy traffic) in questionnaires, walked or cycled all or part of the journey to work, and completed qualitative interviews. Using content analysis of these interviews, we investigated their reasons for walking or cycling. RESULTS: 340 participants reported walking or cycling on the journey to work despite unsupportive conditions, of whom 15 also completed qualitative interviews. From these, three potential explanations emerged. First, some commuters found strategies for coping with unsupportive conditions. Participants described knowledge of the locality and opportunities for alternative routes more conducive to active commuting, as well as their cycling experience and acquired confidence to cycle in heavy traffic. Second, some commuters had other reasons for being reliant on or preferring active commuting despite adverse environments, such as childcare arrangements, enjoyment, having more control over their journey time, employers' restrictions on car parking, or the cost of petrol or parking. Finally, some survey respondents appeared to have reported not their own environmental perceptions but those of others such as family members or 'the public', partly to make a political statement regarding the adversity of active commuting in their setting. CONCLUSIONS: Participants report walking and cycling to work despite adverse environmental conditions. Understanding this resilience might be just as important as investigating 'barriers' to cycling. These findings suggest that developing knowledge of safe walking and cycling routes, improving cycling confidence and restricting workplace parking may help to encourage walking and cycling to and from work.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are