Urban blue spaces support population-level health benefits according to meta-analysisResearch shows that exposure to natural environments in urban settings is linked to improved health and well-being; however, this body of research is largely based on studies of green spaces, and much less attention has been given to the benefits of water environments, or blue space. Additionally, while prior narrative reviews suggest that blue spaces may benefit health, there has been no quantitative analysis of the existing evidence. This systematic literature review and meta-analysis aimed to address these gaps by examining the existing research to quantify evidence of a relationship between blue space and health in urban environments. Importantly, this study provides the first quantitative synthesis of the health impacts of urban blue spaces.
Bibliographic databases were searched to identify peer-reviewed quantitative studies that measured the effects of urban blue space exposure on physical and mental health outcomes. Urban blue spaces were defined to include coasts, rivers, lakes, canals, ponds, and fountains. The search was limited to studies published in English before August 2019. No restrictions were placed on the age of study participants. Studies that examined the combined impacts of blue space and green space exposure were excluded from the review. Studies that investigated virtual reality or images of blue spaces were also excluded. Based on these criteria, 25 studies were selected. Assessment of study quality indicated that the majority were of good quality. The studies were conducted in Europe (13 studies), North America (4 studies), Oceania (4 studies), Asia (3 studies), and South America (1 study). Ten studies focused on physical health, 12 examined mental health, and three considered both physical and mental health outcomes. The majority of studies involved adult participants; however, six studies focused solely on children and young people. The studies mainly used cross-sectional designs. A variety of measures were used to quantify blue space exposure, including objective assessments (e.g., land cover maps and geographic information systems) and self-reported measures (e.g., frequency of visits or travel times to blue spaces). Fourteen of the studies were included in the meta-analysis, which used statistical methods to quantitatively combine results on mortality (3 studies), obesity (3 studies), general health (4 studies), and mental health and well-being (4 studies). The findings of studies that could not be included in the meta-analyses (due to differences in methods or assessed outcomes) were summarized descriptively.
Results of the meta-analysis revealed that living closer to urban blue space was linked to (1) lower obesity levels in adults and children, (2) higher self-reported general physical health in adults, and (3) higher self-reported mental health and well-being in adults. For each of these findings, the combined effect size was small but statistically significant. Additionally, meta-analysis of three studies, with a combined total of 2,067,382 participants, found that the presence of blue space within 500 meters of home was significantly linked to a 1.4% risk reduction in all-cause mortality.
Studies not included in the meta-analyses revealed some instances of mixed findings. A study that examined birth outcomes did not find a significant relationship between waterfront access and children's birthweight. Further, a study found that children who had higher percentages of water near home (within 500 meters) had lower health-related quality of life than those with less water exposure. However, while some mental health and well-being studies did not report significant results, a study involving 17,249 children and young people documented a “significant linear trend” in which higher blue space exposure was linked to improved emotional well-being. Additionally, a study reported that the ability to view blue spaces from home was linked to higher levels of psychological well-being among adults, and another found that adults felt that blue space settings were more restorative than their favorite built urban settings. The majority of studies that investigated depression and anxiety found that blue space was significantly linked to fewer symptoms. One study that examined emotional functioning found that children who spent more time at the beach had fewer peer relationship problems and more prosocial behaviors; however, a relationship was not found between contact with blue space and ADHD symptoms. Another study found no relationship between momentary subjective well-being (mood) and blue space exposure for school students.
Overall findings call attention to the positive impact of urban blue space proximity on health and well-being during childhood and adulthood. Results of the meta-analysis suggest that blue space has beneficial effects on obesity, all-cause mortality, general health, and self-reported mental health and well-being. Although effect sizes were small, the researchers contend that collectively, the positive impact of urban blue spaces can support major public health benefits. Additionally, while the evidence base remains limited and continued research is needed, current results suggest that “blue spaces appear as valuable to public health as green spaces.” Urban planning should leverage the health-promoting potential of urban blue spaces to help create healthier cities. “In the context of the growing worldwide concern for the burdens of non-communicable diseases and mental illness, exposure to urban blue spaces may offer a solution, as part of broader preventative and restorative public health and urban planning policies, to improve urban population health.”
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