Title: Green-blue space exposure changes and impact on individual-level wellbeing and mental health: a population-wide record-linked natural experiment
Funder: Health and Care Research Wales (Welsh Government)

Abstract: This study will investigate how changes in the availability of outdoor green-blue spaces (GBS) have influenced health outcomes over time. We will consider how proximity and accessibility of different types of GBS relate to health benefits in different population subgroups. Using a large scale, population based, natural experimental approach, we will address shortcomings in the evidence base by adding detail on the quality, type, size, and function, to most effectively inform public health, planning and regeneration decisions on the protection and development of GBS for health improvement, enabling future implementation of evidence-based policy. We will use individual-level linked population data to develop statistical models based on theorised pathways through which GBS can affect population health to evaluate the impact of green-blue space (GBS) on subjective wellbeing (SWB), and common mental health disorders (CMD). Hypothesised pathways include the GBS affecting people’s health through both ‘direct’ contact (active engagement through visits) and ‘indirect contact’, (e.g. visual exposure close to home). We will make use of natural experiments to consider multiple longitudinal and spatial variations in exposure, which are impacted by national and local authority policies. We will incorporate detail of these policies into our exposure dataset. We will examine associations between residential GBS exposure and CMD for 1.7 million adults in Wales. We will create a longitudinal quarterly residential GBS exposure dataset for each home in Wales using local authority datasets, collated with guidance from public and policy partners, adjusting for changes in greenness between 2008 and 2018 using remotely sensed data. We will use Ordnance Survey data to extract ‘blue’ features, including canals, ponds, rivers, and beaches; road and footpath network data will be used to calculate distances from each home to residential GBS access points within a 10 minute walk. This will improve on previous studies by increasing exposure-outcome follow up/accuracy by using novel retrospective data linkage methods to incorporate both moving home and in situ changes. Individual-level confounders and effect modifiers will be linked to individuals’ GBS exposures and anonymised-linked routine health outcomes. We will use longitudinal data to explore the association between changes in GBS exposure and routinely collected health data held in an anonymised databank. Analysis will use multilevel models to examine the impact of changing GBS exposure including size, type, quality, and function, on related health outcomes in the adult population, while taking into account individual and regional clustering. A hybrid longitudinal/cross-sectional design will incorporate survey results for 24,000 people to explore the potentially mediating effect of GBS visit frequency on any direct relationship between residential GBS and our data-linked primary health and wellbeing outcomes. Analysis of GBS visits will consider activity type and social factors given their importance for health outcomes. Minimum and optimal green and blue space types accessible from home and within suitable frequent visit distance will be translated with project partners into evidence suitable for policy and practice.

Lay abstract: This study will investigate whether spending time in green and blue spaces, such as parks and beaches, can have a positive effect on our long-term well-being and mental health. Mental health and wellbeing problems are a growing public concern. One in four people experience a mental health condition such as anxiety and depression at some time in their lives. Mental health problems costs the UK economy over £100 billion a year. A growing body of evidence indicates that exposure to green and blue spaces may benefit mental health and wellbeing. Now, the NIHR is investing in a collaboration who will explore whether green and blue spaces, such as parks and beaches, can have a positive effect on our long-term wellbeing and mental health. The collaboration is led by Swansea University Medical School, and involves experts from the University of Exeter, Cardiff University and the Barcelona Institute for Global Health. This new funding will enable researchers to take a large-scale population approach, considering the majority of Wales’ environment and population, and changes over time. The team of academics will work with partners from Natural Resources Wales, Keep Wales Tidy, Sports Wales, City and County of Swansea, and Welsh Government. Researchers will gather health and environment data and link them in a databank based at Swansea University (saildatabank.com). The Secure Anonymised Information Linkage databank (SAIL), is a world-class system that brings data together in a secure, trusted and confidential way. The team will consider how abundance and accessibility of different types of green and blue spaces relate to mental health and wellbeing benefits for different people. Researchers will look at data for 1.7 million people in Wales to explore how people change their use of health services, such as their general practitioner, as their local environment changes. Because the effects of green and blue spaces take time to change health, the team will use historical data with statistical methods to assess the effects over the past decade.

Research activity codes: 3.1 PRIMARY PREVENTION INTERVENTIONS TO MODIFY BEHAVIOURS OR PROMOTE WELL-BEING;3.2 INTERVENTIONS TO ALTER PHYSICAL AND BIOLOGICAL ENVIRONMENTAL RISKS
Health categories: MENTAL HEALTH