The associations between exposure to green and blue spaces with multimorbidity: observational analyses of UK Biobank cohort

Green and blue spaces can protect and promote mental and physical health by mitigating harm, restoring capacities, and promoting physical activity. However, little is still known about the ways different types of green and blue spaces affect the risk of having complex health states, such as multimorbidity. To fill this gap, this thesis examined the relationships between exposure to several types of green and blue spaces with multimorbidity. First, a systematic literature review of longitudinal, observational studies on the relationships between green and blue spaces with long-term mental health conditions and non-communicable diseases (NCDs) was conducted. Results from the systematic review showed there is currently a lack of high-quality, comparative research on different types of green and blue spaces and how they affect the risk of developing long-term mental health conditions and NCDs. A data integration study with European Urban Atlas and UK Biobank was conducted to compute individual-level exposure data on availability of total green space, street trees, inland water bodies, and accessibility to parks. Finally, the cross-sectional associations between these green and blue space exposures with simple, complex, cardio-metabolic, respiratory, and mental multimorbidity were assessed. Results showed that only inland blue spaces moderately reduced the odds of having mental and complex multimorbidity, and that income and physical activity were not strong moderators in these relationships. Although less commonly studied, inland blue spaces, such as rivers, canals and lakes, could offer opportunities for relaxation and mental restoration in all individuals, irrespective of income. Future research should aim to analyse these causal relationships by seeking to understand the underlying biological, social, and behavioural mechanisms. This can inform policy and public health practice. Incorporating blue natural environments into preventative care for multimorbidity can reduce the burden of multimorbidity on health systems and allow individuals to have higher quality of life.