This post highlights 2 recent research papers focusing on the links between health benefits and exposure to green infrastructure.
“Green spaces and cognitive development in primary schoolchildren.” – Dadvand, P., Nieuwenhuijsen, M., Esnaola, M., Forns, J., Basagaña, X., Alvarez- Pedrerol, M., Rivas, I., López-Vicente, M., De Castro Pascual, M., Su, J., Jerrett, M., Querol, X. & Sunyer, J.. (2015). Proceedings of the National Academy of Sciences. 112(26): 7937–7942. DOI: 10.1073/pnas.1503402112
Exposure of primary schoolchildren to outdoor green spaces is linked to an improvement in their cognitive development, finds a new study, which is the first of its kind. The association may be partly explained by reductions in traffic-related air pollution (TRAP) near green areas.
Approximately half of the global population live in cities, and it is projected that by 2030, three of every five persons (60%) will live in urban areas worldwide. Yet urban areas are characterised by increased levels of pollutants and fewer green spaces. Several studies have linked exposure to urban green spaces to improved physical and mental health and wellbeing (1.) Children may be particularly susceptible to the psychological effects of the urban environment, as key cognitive traits are developed during infancy and childhood.
Researchers have now investigated the association between exposure to green spaces and memory and attention in children. They also evaluated the role of TRAP as one of the potential mechanisms underlying this association. This new study took place in the context of the EU-funded Barcelona BREATHE project (2.) which investigates the possible effects of traffic-related air pollution TRAP on brain development in children.
In the 36 primary schools taking part in BREATHE, 58% of children aged 7–10 (2 623) agreed to participate. Children were evaluated four times every three months over a year, using computerised tests to assess their working memory and attention, both of which grow steadily during adolescence. The ‘greenness’ around each child’s home address, within and near their school and along their commute to school was measured using satellite imagery and the Normalized Difference Vegetation Index, a measure of greenness based on reflected light. The values were combined with variables such as time spent in school or at home to estimate each child’s total exposure to greenness. Models were constructed to evaluate the association between green spaces and cognitive development. The research leading to the methodology (PHENOTYPE) used in this study to assess exposure to green spaces received funding from the Commission’s Seventh Framework Programme (3.)
The researchers found that a higher level of exposure to green spaces was associated with improved cognitive development. More specifically, this consisted of a median score of 5% improvement in working memory, 6% increase in superior working memory, and a 1% reduction in inattentiveness. This was attributable specifically for greenness within and near schools. There was no association between residential surrounding greenness and cognitive measurements.
The researchers also investigated whether reduced levels of TRAP could explain the association between green spaces and cognitive development. High-quality data on exposure to the air pollutant elemental carbon (EC) — a tracer of road traffic emissions — in the schools was available through BREATHE. Previous analyses had found lower levels of EC in schools with higher greenness. Adding TRAP exposure to the models explained 20–65 % of the association between school greenness and change in cognitive development. The researchers theorise other mechanisms may include lower exposure to ambient noise and increased physical activity associated with green spaces.
The study provides evidence that targeted interventions such as improving greenness in schools could have significant effects on children’s cognitive development. Based on their study, the authors suggest that if schools with the lowest levels of greenness increased this resource to be on a par with schools with the highest greenness, the number of children with impaired superior working memory development would decrease by 8.8%. The improved cognitive development in children could lead to improved mental capabilities for the rest of their lives. Since this was the first epidemiological study to report on the impact of exposure to green space on cognitive development in schoolchildren, further research is needed to investigate the robustness of these findings. Additional research should explore if similar effects are found during other periods of cognitive development in children, such as prenatal and preschool periods.
Landscape Institute’s, “Public health and landscape: creating healthy places” Position Statement (November 2013). Download A4 version
“Positive health effects of the natural outdoor environment in typical populations in different regions in Europe (PHENOTYPE): a study programme protocol.” – Mark J Nieuwenhuijsen, Hanneke Kruize, Christopher Gidlow, Sandra Andrusaityte, Josep Maria Antó, Xavier Basagaña, Marta Cirach, Payam Dadvand, Asta Danileviciute, David Donaire-Gonzalez, Judith Garcia, Michael Jerrett, Marc Jones, Jordi Julvez, Elise van Kempen, Irene van Kamp, Jolanda Maas, Edmund Seto, Graham Smith, Margarita Triguero, Wanda Wendel-Vos, John Wright, Joris Zufferey, Peter Jan van den Hazel, Roderick Lawrence and Regina Grazuleviciene. British Medical Journal, BMJ Open 2014;4:e004951 doi:10.1136/bmjopen-2014-004951.
Growing evidence suggests that close contact with nature brings benefits to human health and well-being, but the proposed mechanisms are still not well understood and the associations with health remain uncertain. The Positive Health Effects of the NaturalOutdoor environment in Typical Populations in different regions in Europe (PHENOTYPE) project investigates the interconnections between natural outdoor environments and better human health and well-being. This project is a Collaborative Project funded through the European Commission Seventh Framework Programme
Urban planners should be given guidelines to include a minimum amount of green space in cities, according to researchers who have found that exposure to parks and trees helps to prolong life, improve mental health and even increase the birthweight of babies.
Professor Mark Nieuwenhuijsen from the Center for Research in Environmental Epidemiology (CREAL) in Barcelona, Spain, says that access to nature does not merely top up your wellbeing, but it might actually be a necessary condition for good health. Prof. Nieuwenhuijsen coordinates the EU-funded PHENOTYPE project (4.), which is aiming to build up the evidence base for so-called urban greening by understanding how exactly it can influence your health and why. The idea is to feed into decisions made by landscape architects, urban planners and policymakers.
‘Lack of green space causes detrimental health effects,’ he said. ‘Green space is necessary for healthy psychophysiological functioning (and) there could be a set level for good health.’
This is important as more than half of the world’s population lives in urban areas, a figure which is set to grow more than 1 % per year between now and 2030. However, there is currently no agreement on just how much greenery cities should contain for optimal health.
‘At the moment there are no guidelines for green space. It would be nice to be able to give more information to urban planning to make sure that there’s provision of green space. How much green space do you need? There are questions still remaining.’
PHENOTYPE researchers are conducting studies of the health effects of green space in four different parts of Europe: Lithuania, the Netherlands, the UK and Spain. So far they have found that an increase in surrounding greenness leads to higher birth weight for babies, reduced blood pressure during pregnancy, and lower obesity levels in children. They have also found that an increase in surrounding greenness is associated with better mental health and self-perceived physical health. The project is also uncovering suggestions that not all greenery is equal. Prof. Nieuwenhuijsen says that being surrounded by greenery, such as living on streets lined with trees or being able to see vegetation from your office window, may have greater health benefits than having access to a park.
Initial indications are that it is more complicated than the fact that living close to a park could encourage people to take more exercise and lead an active lifestyle. In a study of coronary artery patients in Kaunas, Lithuania, researchers found that people benefitted more from walking in parks than when they did the same amount of exercise but walked on busy urban streets.
Prof. Nieuwenhuijsen says that there is some good evidence that the reason behind this effect could be a reduction in stress levels. ‘There are some studies that show a reduced blood flow in the subgenual prefrontal cortex (which controls stress) when people are exposed to green space.’ Other mechanisms could include a reduction in air pollution and an increase in social contacts. While the exact mechanisms are still under investigation, Prof. Nieuwenhuijsen believes that humans are hard-wired to appreciate the benefits of vegetation.
- The BRain dEvelopment and Air polluTion ultrafine particles in scHool childrEn (BREATHE) was supported by the European Research Council. See: http://www.cordis.europa.eu/project/rcn/99632_en.html
- Positive Health Effects of the Natural Outdoor environment in Typical Populations in different regions in Europe (PHENOTYPE) project was funded through the European Commission Seventh Framework Programme: http://www.staffs.ac.uk/research/
- PHENOTYPE – intended to provide a better understanding of the potential mechanisms, and better integration of human health needs into land use planning and green space management.