A Green Space Agenda: An umbrella review and questionnaire summarising and presenting the evidence and knowledge gaps in the field of green space and health.

Abstract

In the field of green space, many studies have been performed in relation to health. However, not all studied green space is identical. Green spaces can be very different from each other and range from open undeveloped land, to parks, street trees, and nature. The many health outcomes that have been researched are also very different from one another. This combined, creates a very complex body of works, making it difficult for researchers, policy makers and health professionals to clearly see the exact relationships and use green space effectively. This review aimed to present a more complete overview of all the knowledge and knowledge gaps on green space exposure and health outcomes. After a systematic search and critical selection, we included 83 systematic reviews from the last ten years in this project. Additionally, we used a questionnaire to ask various professionals whose work relates to green space on their views and opinions. This served to widen our understanding, and gather new information and viewpoints that are potentially still outside of the published science. We organised the information into eleven categories of health outcomes: Allergies and Respiratory health, Birth outcomes & pregnancy-related health, Cancer, Cardiovascular disease, Cognitive function, General health, Immune system, Mental & neurological health, Metabolic outcome measures, Mortality and lastly, Miscellaneous. There were six categories where study findings pointed mostly to good effects on health without any findings of bad effect on health: Cardiovascular disease, Cognitive function, General health, Metabolic outcome measures, Mortality and Miscellaneous. For immune system, we found that just under half the study findings were of good effects on health. The other findings pointed to no or unclear effects. Two categories had mostly good study findings, but also findings on no effects and even a few bad effects on health. These were Birth outcomes & pregnancy-related health, and Mental & neurological health. In the last two categories, Cancer and allergies & respiratory health, many study findings pointed to no effects, some to good effects and a few to bad effects on health. To fully make these finding useful and practical, good understanding of how these effects are caused is needed. This can allow policy makers and heath professionals to adopt green space exposure as a way to prevent, delay, or treat diseases. In this review, we have outlined the gaps in our understanding and present these for research to let it guide their future efforts. We found that attention to theoretical foundations, methodologies, socioeconomic position, and health inequalities can be useful to improve our knowledge on the complex relationships between green space exposure and health outcomes in general. We have also summarised many knowledge gaps specific to our eleven health outcome categories and even added one more: Childhood development. We present these knowledge gaps so that future studies might be directed towards filling in these gaps. In conclusion, we have summarised the study findings included in 83 systematic reviews. Most findings point towards positive effects of green space exposure on health. However, more studies are needed to confirm and better understand these relationship.