Abstract
Introduction: Urbanisation, defined as a mass relocation mechanism of populations towards urban settlements, constitutes a significant hurdle for urban planning, which is thought to widen the socio-economic and health inequalities in cities. These inequalities often co-exist with climate change risks, which primarily affect the most vulnerable groups of our societies. Nature-based solutions, such as green (parks, gardens, woodlands, and other vegetation-rich areas) and blue spaces (all visible waterbodies, such as lakes, rivers, ponds, canals, and coastal water) have been proposed as potential tools to narrow the inequality gap, improve public health, and make living in cities healthier and more sustainable. While most research has focused on green spaces, research around the potential effects of blue spaces on health is still at its early stages and is rapidly emerging. Some studies have shown that blue spaces could have significant salutogenic and equigenic effects, but the mechanisms of these effects, their longitudinal persistence and the overall cost-effectiveness of blue settings are yet to be determined. This thesis aimed to: (1) investigate and quantify the mechanisms of the impact of urban blue space on health and health inequalities, (2) study the effects of blue spaces longitudinally with a particular focus on mental health and the role of socio-economic deprivation in the development of mental health conditions, (3) translate the effects of urban blue space on mental health in monetary terms and therefore progress understanding towards the potential returns of blue space regeneration efforts.Methods: To achieve these aims, three studies were conducted. A systematic review and meta-analysis study was initially performed to synthesise evidence around the mechanisms of the impact of blue spaces on health and quantify the effects of each pathway (Study 1). Four proposed mechanisms were investigated, namely (1) physical activity, (2) restoration, (3) social interaction and (4) environmental factors. This included a systematic search of six databases (PubMed, Scopus, PsycInfo, Web of Science, Cochrane Library, EBSCOHOST/CINAHL), following the PRISMA guidelines. Subsequently, random-effects meta-analyses were conducted for the pathways with enough data available, namely physical activity, restoration, and social interaction. A meta-analysis was not possible for the environmental factors proposed pathway due an insufficient number of studies available. Next, a longitudinal population-based retrospective study over a 10-year period was conducted to investigate the effect of urban blue space on mental and its relationship with socioeconomic deprivation, during the large-scale regeneration of an urban blue space (canal) from complete dereliction and closure, in Glasgow, Scotland (Study 2). The analysis of this study used longitudinal routinely collected primary care National Health Service (NHS) data and included 132,788 people (65,351 female). A base model estimating the effect of socio-economic deprivation on the risk of developing a mental health condition was initially established, using a Cox proportional hazards model, adjusted for age, sex and pre-existing comorbidities. A similar second model was then developed with the addition of a distance to blue space variable to investigate the modifying effect of living near blue space. The blue space mental health outcomes found in this study were later translated into monetary terms in a separate large Monte Carlo population-based valuation study (Study 3). Study 3 used the same NHS database of routinely collected primary care data, over the same 10-year period of a large-scale regeneration of an urban blue space in Glasgow, Scotland.
Results: Study 1 found that physical activity, restoration and improved environmental factors were indeed the main mechanisms of the impact of urban blue spaces on health. Specifically, living closer to blue space was associated with statistically significantly higher physical activity levels (Cohen’s d = 0.122, 95% CI: 0.065, 0.179). Larger amounts of blue space within a geographical area were significantly associated with higher physical activity levels (Cohen’s d = 0.144, 95% CI: 0.024, 0.264) and higher levels of restoration (Cohen’s d = 0.339, 95% CI: 0.072, 0.606). Being in more contact with blue space was also significantly associated with higher levels of restoration (Cohen’s d = 0.191, 95% CI: 0.084, 0.298). There was also consistent evidence that blue spaces lead to improved environmental factors, while evidence for the social interaction pathway was conflicting. Study 2 found that living near blue space modified the risk of developing a mental health condition due to socio-economic deprivation by 6% (hazard ratio 2.48, 95% confidence interval 2.39–2.57) for those living in the most deprived tertile (T1) and by 4% (hazard ratio 1.66, 95% confidence interval 1.60–1.72) for those in the medium deprivation tertile (T2) of the analysis. Study 3 found that regardless of how close or far one lived from blue space, the negative impact of socio-economic deprivation on mental health remained significant. Socio-economic deprivation accounted for a large portion of the loss in quality of life, measured in Quality Adjusted Life Years (QALYs) and in monetary terms. However, living within 1km proximity to blue spaces was found to have a positive impact, resulting in a total benefit of 339.41 QALYs or a monetary value of £6,788,164, among those in the most deprived and medium deprivation neighbourhoods of the North Glasgow Forth and Clyde canal surrounding area combined, over the 10-year study period.
Conclusion: Overall, the findings of this thesis clarified the mechanisms of the blue space effects on health and indicated that blue spaces mainly benefit human health by increasing physical activity, boosting restoration, and improving environmental factors. Focussing on mental health, the blue space salutogenic effects were found to persist longitudinally, however, rather than directly, these effects were found to mainly derive from the attenuation of the adverse impact of socio-economic deprivation. This work concludes that blue space regeneration efforts can potentially constitute a strong tool to improve public health and battle health inequalities in cities. Investing in the regeneration of blue spaces could return a significant portion of the initial monetary investment to the adjacent communities in the form of wellbeing and, if proven economically and clinically effective, blue space settings could be considered therapeutic sites for the treatment of mental health conditions.
| Date of Award | 2023 |
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| Original language | English |
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| Supervisor | Sebastien Chastin (Supervisor) & Gordon Morison (Supervisor) |