There is growing interest in the ways natural environments influence the development and progression of long-term health conditions. Vegetation and water bodies, also known as green and blue spaces, have the potential to affect health and behaviour through the provision of aesthetic spaces for relaxation, socialisation and physical activity. While research has previously assessed how green and blue spaces affect mental and physical wellbeing, little is known about the relationship between these exposures and health outcomes over time. This systematic review summarised the published evidence from longitudinal observational studies on the relationship between exposure to green and blue space with mental and physical health in adults. Included health outcomes were common mental health conditions, severe mental health conditions and noncommunicable diseases (NCDs). An online bibliographic search of six databases was completed in July 2020. After title, abstract and full-text screening, 44 eligible studies were included in the analysis. Depression, diabetes and obesity were the health conditions most frequently studied in longitudinal relationships. The majority of exposures included indicators of green space availability and urban green space accessibility. Few studies addressed the relationship between blue space and health. The narrative synthesis pointed towards mixed evidence of a protective relationship between exposure to green space and health. There was high heterogeneity in exposure measures and adjustment for confounding between studies. Future policy and research should seek a standardised approach towards measuring green and blue space exposures and employ theoretical grounds for confounder adjustment.

Urban greenspace provides opportunities for outdoor exercise and may increase physical activity, with accompanying health benefits. Areas suitable for walking (walkability) are also associated with increased physical activity, but interactions with greenspace are poorly understood. We investigated associations of walkability and green walkability with physical activity in an urban adult cohort. We used cross-sectional data from Greater London UK Biobank participants (n = 57,726) and assessed walkability along roads and footpaths within 1000 m of their residential addresses. Additionally, we assessed green walkability by integrating trees and low-lying vegetation into the walkability index. Physical activity outcomes included self-reported and accelerometer-measured physical activity and active transport. We assessed associations using log-linear, logistic and linear regression models, adjusted for individual- and area-level confounders. Higher green walkability was associated with favourable International Physical Activity Questionnaire responses and achievement of weekly UK government physical activity guideline recommendations. Participants living in the highest versus lowest quintile of green walkability participated in 2.41 min (95% confidence intervals: 0.22, 4.60) additional minutes of moderate-and-vigorous physical activity per day. Higher walkability and green walkability scores were also associated with choosing active transport modes such as walking and cycling. Our green walkability approach demonstrates the utility in accounting for walkability and greenspace simultaneously to understand the role of the built environment on physical activity.

BackgroundGreen and blue spaces can promote good physical and mental health and prevent the development of long-term conditions. Evidence suggests that not all green spaces affect health equally, and that certain types and properties of green spaces are stronger predictors of health than others. However, research into the causal mechanisms is limited in large cohorts due to lack of objective and comparable data on green space type, accessibility, and usage.MethodsWe used data from Urban Atlas to compute measures of urban park accessibility, street trees availability, and total green and blue space availability for 300,000 UK Biobank participants. Exposure metrics were computed using circular buffers with radii of 100 m to 3000 m. Pearson correlation coefficients and other descriptive statistical parameters were used to test agreement between variables and explore the utility of indictors in capturing different types of green spaces.ResultsStrong positive correlations were observed between variables of the same indicator with different buffer sizes. The presence of park and proportion of street tree canopy variables were negatively correlated with amount of total green space variables. This signifies distinct differences in type of green spaces captured by these variables.ConclusionsOverall, five distinct indicators of park accessibility, street trees availability, and total green and blue space availability have been integrated into a large sample of the UK Biobank. Our method is replicable to settings across Europe and facilitates evidence-based research on the roles of different green and blue spaces in health promotion and ill-health prevention.Key MessagesDifferent types of green spaces and their position in the neighbourhood can promote and protect health by mitigating pollution and increasing physical activity and socialisation.We present the methods of constructing and linking data on urban green spaces, street trees and natural vegetation into a large health cohort, the UK Biobank.The ability to distinguish between types of green spaces and their intended use can help inform public health interventions, influence urban policy, and aid urban planning in building sustainable and healthy cities.Our methods are transferable and will allow others to explore the links between environment and health in UK Biobank and other health cohorts.