Discussion

Introduction

Low physical activity is widespread and poses a serious public health challenge both in the UK and worldwide.251 The need to increase population levels of physical activity is recognised in current health policy recommendations.5,252 However, interventions to increase physical activity levels, particularly community-wide interventions, have shown limited effects that are poorly maintained in the longer term.29 There has been increasing interest in whether or not the built environment, especially in urban settings, might be a key constraint that limits opportunities for physical activity.31 However, there is very limited high-quality experimental evidence examining the influence of change in the built environment on physical activity.30,31 The ENABLE London project was established to address this issue, by providing evidence from the investigation of a natural experiment examining whether or not a sizeable change in the built environment can increase physical activity levels, as well as indicators of both physical and mental health, in the general population. This question has important public health relevance as small shifts in population levels of physical activity, in addition to other markers of health, can have an appreciable impact on health-related outcomes.253

Principal findings

The East Village development, a neighbourhood repurposed in accordance with active design principles, resulted in sizeable improvements in objective measures of the built environment and neighbourhood perceptions of the local built environment among those who moved there compared with those who did not. However, after 2 years, moving to East Village did not have any consistent beneficial effects on objectively measured physical activity, adiposity or other health-related outcomes of public health importance. Although modest reductions in car travel and increased use of public transport were observed among those who moved to East Village, these did not materialise in demonstrable change in active modes of travel (i.e. time spent walking or cycling). These findings suggest that the built environment is insufficient on its own to change physical activity behaviour. More evidence from similar longitudinal studies is needed to confirm these findings. However, given the difficulties and costs of this type of study, which relies on urban regeneration, we may need to think of innovative approaches to evaluate the effect of housing and urban change developments on health, to inform future evidence-based housing policy.

Principal contributions and implications of the study

Explaining the effects of the intervention

Understanding the mechanism through which the built environment might influence health behaviour is not straightforward and may well be multifaceted.96 Reasons for the lack of clear effects of the East Village development, the ‘intervention’, on the physical activity-related behaviour of residents remain to be fully understood,33 especially when findings from cross-sectional studies are less equivocal.93 One potential explanation is that those seeking to move are inextricably different from those who do not. The ENABLE London study sought to minimise this bias by recruiting a cohort of individuals seeking to move to East Village, which we believe, in the absence of randomisation, offers the best possible study design. It is also possible that the magnitude of change in the built environment was insufficient to induce a major change in physical activity. However, the East Village development showed marked changes in objective GIS-derived markers of the built environment and sizeable improvements in neighbourhood perceptions (particularly in perceptions of crime and quality) among residents moving to the area compared with those who did not move or moved elsewhere. So why did the change in the built environment not result in a bigger change? This report ventures a number of explanations, including whether exposure to the environment was long enough or sufficient enough to induce the change expected; the environment was incomplete when the first social housing residents moved in and was compromised by further high-rise development and loss of green space more latterly.218 In the absence of more discernible effects on health and behaviour, it is difficult to establish clearer explanations for the lack of more definitive findings. However, it appears that the built environment alone is insufficient to induce the change in health behaviour expected by passive means and that more interactive strategies, perhaps in conducive environments such as East Village, are needed (i.e. perhaps higher-agency programmes combined with low-agency environments are needed to induce change). However, although high-agency population interventions are often used, particularly by governments to improve diet and reduce obesity, they are often ineffective254 with time constraints and low levels of motivation often being cited as reasons for poor uptake.255 Moreover, high-agency interventions that require more effort from the individual may reinforce or even worsen socioeconomic inequalities in health.254 Hence, low-agency interventions that require less investment from the individual may be more effective, having a small effect in greater numbers and hence may be more equitable by having greater reach.254 In the context of East Village, greater agency could be achieved through greater awareness among the residents of the activity-inducing features and facilities that exist (such as walkways, cycleways and sporting venues) and fostering the belief, particularly among social tenants, that these are available to all. However, the premise of this study was to examine the effect of the built environment per se, without these additional ‘nudges’ to promote use.256

Generalising the effects of the intervention

In terms of the representativeness of the ENABLE London cohort, we compared our physical activity data at baseline to a nationally representative study, the Health Survey for England,257 that used a similar methodology: the same waist-worn accelerometer (ActiGraph) worn for an equivalent wear time (1 week). Adults aged 16–34 years from this study recorded 40 minutes per day in MVPA, of which, on average, 15 minutes was in 10-minute bouts. Our baseline data suggest comparable levels of activity among those of a similar age in the social sector with 47 minutes of daily MVPA and 7 minutes in bouts (with an IQR between 1 and 15 minutes), but higher levels among those in the intermediate and market-rent sectors with 65 minutes of MVPA and > 20 minutes recorded in bouts. Although this suggests differences in baseline physical activity levels across the housing sectors in the ENABLE London cohort, there was no evidence of a trend across other social markers (i.e. income groups) in the Health Survey for England study. Moreover, the greater change in physical activity associated with moving to East Village in the intermediate and market-rent tenured groups compared with those in social housing, does not suggest that these higher levels (albeit not significantly higher) limited scope for change (i.e. participants from these non-social tenured groups had reached the capacity for further increases). In terms of geographic patterns in physical activity, reanalysis of the Health Survey for England7 data did not suggest that self-reported higher levels of physical activity in London were unduly higher or lower than other government office regions.258 Hence, we believe that null findings from the ENABLE London study do not reflect bias within our cohort and are transferable beyond our study population. However, it is acknowledged that a cohort of ‘movers’ seeking to move to East Village, an active permissible space being built on active design principles, were targeted for the study and their activity patterns may differ from the population at large. Hence, this may have some implications for the generalisability of the findings.

In terms of specific features of the East Village development that could have influenced health and well-being (such as the use of pathways, cycle paths, links to public transport, open spaces and leisure facilities) are (or could be) features of many built environment developments. Hence, we believe that findings from this study have substantial potential for wider generalisability to other urban areas. An ultimate goal of the project was to identify evidence-based design features of the built environment that encourage physical activity and improve health behaviours. It was hoped that the identification of these environmental features would provide architects, urban designers and planners with evidence-based urban design elements, which are required for future developments.

We hope that findings from the ENABLE London study will be generalisable to other urban residential housing developments, especially given the urgent need for higher-density housing, and will help inform evidence-based urban planning in future.

Methodological investigations and development

We believe that the ENABLE London study design that we have developed offers a robust test of the effect of the built environment on physical activity and health behaviour, in the absence of randomisation. We did explore carrying out randomisation of accommodation with Triathlon Homes, a partner organisation of housing associations, which manages social and intermediate homes in East Village, but unfortunately this was not feasible. Hence, the approach used offers the next-best alternative. The richness of the data recorded, although making participation and data collection more onerous, provided an excellent opportunity for novel exploration. The development of an automated method of recording travel mode journeys from combined accelerometry and GPS data allowed change in active forms of travel to be examined in an objective automated way, which would have been prohibitively lengthy using previous manual approaches.48,49 The tool developed (outlined in Chapter 5) has been validated in the cohort (as well as in a separate study) and although it showed little change in active forms of travel (i.e. walking and cycling), consistent with no overall change in physical activity levels (see Chapter 3), it showed modest reductions in car travel and an increased use of public transport (i.e. underground), which was associated with moving to East Village. These methods have been published and made available for use by the wider scientific community, offering an ongoing legacy from the work.

Engagement with patient and public involvement/stakeholders

The ENABLE London study was developed in partnership with a network of both local and regional stakeholders identified through our collaborator links to agencies, which were involved with the design, planning and management of large-scale accommodation developments. Locally, these included local authorities (particularly Newham) and a number of housing associations, in particular the East Thames Group and Triathlon Homes (which continue to be responsible for social and intermediate tenured housing in East Village). Open meetings held by the East Thames Group and Triathlon Homes were attended by the investigators at an early stage of the project, to directly interface with those contemplating moving to East Village, to establish the drivers and reasons for considering moving to East Village, and to ensure that these were fully captured in the forms of assessment. Moreover, qualitative work was also convened early on in the project to gauge experiences among those who were the very first to move to East Village, so that follow-up examinations could be adapted to ensure that all relevant areas were covered, and that assessments and participation remained engaging and enjoyable, and to ensure the continued significance and potential generalisability of the work. Another key aspect of engagement/stakeholder involvement was attendance and presentation at national and international conferences and special stakeholder workshops, particularly those convened by the Town and Country Planning Association at an early stage of the project, to encourage further stakeholder participation and to share experiences with other researchers carrying out similar work; this provided the opportunity for ENABLE London study methods to be refined and optimised. Similarly, publications to date, particularly those describing study methods and baseline data, also provided opportunities for further dissemination and potential input from those working within the field. The investigators continue to be in contact with representatives of the Town and Country Planning Association, Public Health England and the London Borough of Newham not only to disseminate findings from the ENABLE London study but, more importantly, to inform the future direction of research in this area, with the goal of providing stakeholders, architects and planners with the evidence base needed to inform future housing developments.

Challenges, strengths and limitations of the study

Challenges of the study

The ENABLE London study provided a unique opportunity to observe a ‘natural experiment’ to assess the impact of a rapidly changing built environment, specifically designed to encourage walking and cycling, on the physical activity patterns of residents. Natural experiments are associated with a number of challenges that are often out of the control of the researchers. Our original plan, as specified in our bid for funding, was to carry out the baseline recruitment between January 2013 and mid-2014 and then to follow up participants after 1 year, between January 2014 and mid-2015. However, there were marked delays in the release of East Village accommodation, which resulted in a prolonged period of recruitment from January 2013 to January 2016. In addition, the delayed opening of East Village facilities (a crucial element of the East Village environment and the natural experiment under evaluation) led to a postponement of the follow-up assessment from 1 year to 2 years. The scientific case for delayed follow-up was strong in that (1) East Village was not fully open for use in 2014 when first follow-up was initially envisaged and (2) previous studies have suggested that it takes 2 years as opposed to 1 year for habitual levels of physical activity to change in response to a changed built environment.44 The scientific rationale for 2-year follow-up was approved by our Trial Steering Group. As a result, the timing of the follow-up examination (originally envisaged to take place between January 2014 and mid-2015) began in February 2015 and was completed in October 2017. We remained adaptive to these challenges throughout the study by modifying the working hours of field workers in response to demand (particularly making use of part-time as opposed to full-time appointments) to ensure that the research funding that was awarded covered the extended period of fieldwork. However, the prolonged period of fieldwork inevitably resulted in difficulties in consistency of the exposure to the built environment, which, as outlined above, was underdeveloped at first follow-up, becoming fully open and then more latterly overdeveloped from what was initially envisaged (see Limitations of the study). Moreover, the high levels of rental tenure in East Village resulted in a more mobile population, and many of the intermediate and market-rent occupants who took part in the study have since moved away from the area.

Strengths of the study

The building of East Village provided an important novel opportunity to evaluate a ‘natural experiment’ based on the major and focused change of an inner-city urban built environment that has been specifically designed to encourage walking, cycling and healthy living. It is also unique because the study included residents from widely differing socioeconomic backgrounds. Although many developments of this scale are under way or are being planned in cities globally, few have been (or are being) evaluated and most are less easily evaluated given that the timescale of their development is much longer than in the case presented by East Village. The rapid occupancy of this development was a major strength, providing the opportunity for pre and post assessment and to compare 2-year change in health outcomes among those who did and did not move to East Village. The different housing tenures within East Village also allowed for the evaluation of socioeconomic position as an effect modifier, as the impact of the built environment may vary by socioeconomic position. The focus on increasing levels of accessible and low-cost forms of physical activity remains particularly relevant to individuals and households of lower socioeconomic status and has the potential to inform efforts to reduce health inequalities.259 This allowed us to examine whether or not the built environment favourably influenced higher levels of physical activity (particularly walking and cycling), as well as reducing time in sedentary activities, particularly among low-income groups with fewer opportunities for recreational activities.259 Moreover, the co-location of this diverse population of differing housing tenures to one community also constituted a social experiment, providing opportunities for residents to observe and learn from the behaviour of others.260

Another key strength is that the study sought to recruit a cohort who were seeking to move, half of whom succeeded and half of whom did not, which avoided potential biases in health behaviour. In the absence of randomisation, we believe that this study design offers the next-best alternative, providing less biased and more robust evidence about the potential effect of the built environment on health-related behaviours and outcomes. Following the same individuals before and after any move to East Village also offers statistical efficiencies in that individuals act as their own controls, which eliminates confounding factors that do not change within subject.261,262 Moreover, the consistency of effects using 1 or 4 days of objectively measured physical activity allays fears about potential selection effects associated with using fewer days of recording, which were needed to maximise the number of study participants, particularly among the harder-to-reach social housing sector. The use of accurate objective assessment of physical activity is another strength, including assessments of MVPA that underpin current physical activity recommendations;4 this allows the potential public health importance of the findings to be gauged. However, effects on MVPA were small, suggesting that the change in the built environment had limited impact in achieving current physical activity recommendations, which focus on higher levels of activity.4 Objective assessment of physical activity assessment reduces measurement error and potential biases arising from self-reported levels of physical activity,88 which could be artefactually associated with moving to a new environment being advocated for healthy active living. Furthermore, we have recently published a paper comparing the effect of a successful pedometer-based walking intervention on change in physical activity observed from accelerometry and IPAQ forms of assessment, and have shown that the change in physical activity was estimated with far less precision compared with the hip-worn accelerometry form of assessment.263 Hence, use of the IPAQ data would lead to greater uncertainty about the findings, which already show no clear evidence of effect. Similarly, objective measures of adiposity using validated measures of bioimpedance minimise measurement error and limit any potential biases in ascertainment, particularly among a multiethnic population.264,265 The ability to examine different socioeconomic groups allows social inequalities in effects and potential determinants to be examined.266 Although there was the suggestion that change in physical activity was greater in the intermediate sector than in the social housing and market-rent groups, there were no clear differences observed by housing sector, emphasising that the study was underpowered to formally examine impacts on health inequalities.

Limitations of the study

A key limitation was that the study was powered to detect a 750-step difference.61 Hence, the study was underpowered to show that the change in steps observed associated with moving to East Village compared with the control group was statistically significant overall (i.e. 154 steps, 95% CI –231 to 539), let alone in housing tenure subgroups with fewer participants. Effects on MVPA associated with moving to East Village (particularly in ≥ 10 bouts, commensurate with current UK physical activity guidelines)4 were small and uncertain (i.e. effect estimates were associated with wide CIs). Limitations in sample size were a result of the modest participation rates (50–60%) and unforeseen restrictions on recruitment, particularly among the market-rent sector.61 Moreover, the staged recruitment in which those in the social sector were moved in first when East Village was not fully completed, may have resulted in partial exposure to the physical activity promoting environment and before residential density had reached capacity, which may have limited the full impact of the exposure.61 This was partly a reason for follow-up after 2 years rather than 1 year, but also because previous work has suggested that longer durations are needed for habitual health behaviours to evolve and to avoid early ‘honeymoon’ effects44,267–269 or, conversely, for residents to become fully familiar and make optimal use of their residential area.148 The RESIDE study found stronger differences over time, as suburbs evolved and new facilities were built and habits became more established.95 Further follow-up could plausibly demonstrate beneficial effects but given the mobility of the cohort and the fact that the study is underpowered these are unlikely to yield statistically significant findings. Moreover, East Village is evolving and the building of high-rise accommodation (> 30 storeys) among the existing 10- to 12-storey accommodation, and subsequent loss of green space, may dampen exposure effects even further.218

Information on social environmental factors, including qualitative research exploring the lived experience of residents, may help to explain why residents of this new area did not respond to an environment designed to be health promoting. It is plausible that the facilities provided did not meet the needs of the new residents and/or they did not feel welcome to use those facilities, especially social housing participants.233 This requires further exploration. However, another reason why effects were not more evident might be that London is largely a ‘green city’, especially in relation to other capital cities,270 limiting the opportunities to detect change if controls moved to an equally good space. However, the effect was in fact marginally strengthened when comparing East Village with controls who moved elsewhere and the difference was reduced when comparing East Village with controls who remained at their baseline address, suggesting that this is not the case. There was also no effect of moving to East Village on adiposity levels, and no effect on mental health and well-being outcomes of public health importance.

Another limitation was the adult focus of the study, as East Village did not attract as many families as anticipated, leading to a limited number of children being recruited to participate in the study. This was also evidenced by the Chobham Academy, originally designated to educate children moving to East Village, having to increase the catchment area to fill its pupil capacity. This was an unforeseen circumstance, out of the control of the researchers, which resulted in the study being underpowered to determine any change in physical activity and health behaviours associated with moving to East Village among this age group. Hence, this limits the generalisability of the findings, particularly to younger age groups.

Implications for future research

Although it remains plausible that the built environment alters physical activity patterns and other health behaviours, this study suggests that the effects may be small, particularly, as in this case, when people relocate into new high-density neighbourhoods. There are many discussions globally about the health impacts of high-density urban living, particularly high rise, and there is an urgent need to mitigate potentially adverse consequences.26 However, this does not mean that a small effect across a whole population is unimportant. In contrast to other community-wide interventions, which have shown limited effects on physical activity,29 change in the built environment potentially has greater reach. Even though there were modest effects on MVPA, potentially a 400 step per day change (observed in the intermediate group) across the whole population could have appreciable effects on health outcomes at a population level, potentially reducing all-cause mortality by 2% (95% CI 1% to 4%).271 However, further evidence is required, particularly about the factors that resulted in social housing residents who relocated actually decreasing their level of physical activity. Such studies would have to be large in scale, larger than the ENABLE London study, to demonstrate change. As availability and affordability of housing is a pressing concern, particularly in major conurbations such as London, and the environments in which we live and the accompanying social context have been shown to be related to physical activity levels (including higher levels of physical activity),104,272 more studies evaluating the effect of large-scale housing redevelopment and/or new development programmes are needed to inform the debate about future housing policy. These studies should be diverse in nature to encompass high-density as well as low-density housing. Moreover, suitability and attractiveness of these housing types to different populations (young and old, different tenures and income groups) should be considered to improve the generalisability of potential findings, whether these be favourable or otherwise.

Although there is a strong scientific case for such large-scale studies, challenges of funding, especially in the current economic climate, will limit opportunities. Hence, novel approaches using simulation studies or alternative low-cost forms of population surveillance may be needed to make such large-scale studies viable.

Conclusions

There is a need to shift from the paradigm of cross-sectional studies to stronger research longitudinal designs that make use of large-scale residential relocation opportunities. Natural experiments that make use of circumstances in which people relocate to a new built environment are ideal.41,83 However, despite the growing need for housing, especially in major conurbations such as London,273 opportunities for such studies are limited. Challenges include the need to identify and engage with proposed developments from an early stage, the need to obtain access to those planning to move well before any move occurs, the need to recruit sufficient participants, the unpredictability of creating environmental interventions as planned, and the need for flexible funding to adapt to unforeseen delays given the researchers lack of control over any potential build. Only by assimilating evidence from such studies conducted in different types of neighbourhood, which employ common methodologies that can be directly combined, can the effect of the built environment on physical activity be fully elucidated and understood to inform the planning and provision of housing for optimal health.