Main findings
To our knowledge, this is the first systematic umbrella review on the relationship between specific urban interventions in the built environment and PA. We identified 16 interventions (divided into three categories) of which seven were promising: park renovations, adding exercise equipment, introducing a new (pocket) park, improving cycling environments, improving both walking & cycling environments, multi-component initiatives for active travel, and enhancing availability & accessibility of destinations. Each of the three intervention categories, namely park and playground interventions, interventions aimed at walking and cycling and community-based interventions, showed at least one promising intervention. Therefore, we conclude that all three intervention categories have the potential to contribute to the promotion of PA.
In the category of park and playground interventions, renovation of parks (e.g., upgrading paths, adjusting seating areas, adding barbecue or picnic areas, etc.) was positively related to PA. Although playground renovation was found less effective, this intervention was reported by only two primary studies. The combination of park & playground renovations showed less impact than park renovations alone. This might be explained by the fact that playgrounds are mostly used by children, and two of the three reviews that reported on park & playground renovations made no distinction between age groups. This combination of renovations might therefore show a less positive effect, because it has less impact on older age groups. Other interventions that can promote PA include adding exercise equipment (e.g., fitness equipment and family fitness zones) and a new (pocket) park. It can therefore be concluded that introducing new destinations or facilities is beneficial for promoting PA. Multi-component green initiatives were found to have no effect on PA. However, the outcome of this intervention was based on only one of the included reviews, and further evidence is required to fully evaluate the effectiveness of this intervention.
In the second intervention category, interventions aimed at walking and cycling, the intervention improving solely the walking environment showed mixed results with half of the BE changes showing a positive effect and half a null effect. In contrast, interventions addressing a combination of BE changes were more promising to promote PA, being multi-component initiatives for active travel and improving walking & cycling environments. Therefore, we argue that in this case it is more promising to promote PA with combined interventions. Strikingly, however, interventions focusing solely on improving the cycling environment also show promise to improve PA. We thus learn that more comprehensive interventions are mostly more effective with the difference in effectiveness between walking and cycling interventions requiring further study.
In the community-based intervention category, only interventions enhancing availability & accessibility of destinations had a positive impact on PA. This finding is in line with a previous umbrella review, which found enhancing overall access to facilities and access to public transport to have positive effects on PA [32]. Enhancing density, which has been recognized as an important indicator for PA [33–35], however, showed fewer positive effects in our results. This difference in outcome might be caused by different measuring methods. Increasing density alone (e.g., housing density) might not lead to an increase in PA [36], but often when an area gains density, other functions or destinations are also added or increased, and those do have a positive effect on PA. It can therefore be argued that density itself does not have actual impact on PA, but a positive impact can be shown when increased density is combined with more diverse land use or more access to varied destinations. Finally, street network initiatives showed mixed, mostly null, outcomes, which contradicts findings from other studies where it was found to have a positive effect [32, 33]. This contradiction might be explained because street network initiatives is a very broad term that can include many different interventions, meaning that different studies may have investigated different initiatives under the same name.
The findings from this systematic umbrella review showed that all three intervention categories included interventions that can promote people’s PA levels. Even so, it remains difficult to explain why some interventions work and others do not, especially when interventions seem comparable, such as park renovations and park & playground renovations or improving walking environments and improving cycling environments. The insufficiency of evidence on the effectiveness of intervention for increasing PA is also reported in the Guide to Community Preventive Services [37]. This points out that designing urban interventions to change people’s behavior is very challenging and the same is true for researching those interventions [38]. Certain interventions may be effective in a certain context or environment but might not work in other instances.
Strengths and limitations
The main strength of our systematic umbrella review is that we focused on studies that measured PA levels before and after intervention, providing relatively strong evidence for a causal relationship between the urban intervention and PA. Most previous umbrella reviews on this topic include cross-sectional studies, limiting the potential for inferences on causal relationships [32]. Our systematic approach and umbrella review strategy led to a comprehensive overview of the evidence. The included studies were all moderate and high quality, which led to reliable outcomes.
Our review has potential limitations. First, some methodological limitations were identified among the included reviews, such as low-quality primary studies that lacked methods to minimize errors. In this umbrella review, however, we could not further adjust for this within the included reviews. Nonetheless, our quality assessment showed an overall moderate-to-high quality of included reviews. Second, we synthesized evidence from studies worldwide, without differentiating for local context. Our findings may thus have been affected by the heterogeneity of settings. Furthermore, the measuring standard and the definitions for both interventions and PA varied across the studies, which might have impacted our findings. Some included reviews showed only if an intervention had an effect in the expected direction (i.e., a positive or a null outcome), not whether it had a negative effect [24], while other reviews did. This may have impacted the null and negative outcomes slightly but should have no influence on the positive outcomes. Finally, our findings are based on all age groups combined even though the impact of some interventions might vary across ages. However, we cannot report on evidence per age group, as not enough reviews reported on this.
Implications for practice and policy
As we focused on specific urban interventions, the three intervention categories identified in our paper can be directly useful for practitioners and policymakers in the planning of urban interventions to create health-promoting environments. However, urban interventions are context-related and often multi-interpretable due to the variations in their definition which may help to explain inconsistencies in the evidence. This has implications for the contribution of robust scientific evidence to date on practices and policies to inform health-promoting environments. There is, however, a growing body of knowledge on how urban interventions are associated with PA which should be considered by urban design practitioners.
Implications for future research
We found some conflicting findings, possibly due to methodological limitations of the included reviews, such as combining geographical contexts and age groups and the limited quality of some of the primary studies. This implies that to gather knowledge on what works where, future research findings should be differentiated for context, e.g., for demographics and environmental characteristics of an area or region. There is no ‘one size fits all’ approach; interventions need to be tailored based on local contexts and population needs.
In addition, our findings on street network initiatives conflicted with previous studies, possibly due to differing definitions. This shows the need to standardize terminology; consistent definitions and data synthesizing of ‘interventions’ and ‘physical activity’ is required for further research. Without standardization, the interpretation of the findings cannot offer strong support to causal relationships between PA and BE. We found very little evidence based on low-income countries, and it is well documented that low-income countries have higher rates of disease resulting from inactive lifestyles [39]. More research on low-income countries is needed. More longitudinal research with a pre- and post-measurement is needed to provide a better understanding of the causal relationship between urban environments (or the built environment in general) and population PA. There is a need for more high-quality studies to provide more conclusive evidence.
