Literature review points to association between long-term exposure to green space and cognition

This systematic review of the literature sought to identify available evidence on the association between long-term exposure to green space and cognition covering all stages of life. While previous reviews have reported evidence of the health-promoting effects of exposure to natural environments, none have focused on the association between long-term exposure to green space and cognitive function through the life course.

Thirteen studies met the selection criteria for this review. A quality assessment was then conducted on each of the studies by two reviewers working independently. A quality score was assigned to each of the studies placing each in one of five quality categories: excellent, good , fair, poor, and very poor. Studies were also classified in relation to level of evidence for a causal relationship between the exposure to green space and the reported outcomes. For this classification, the researchers applied the guidelines used by the International Agency for Research on Cancer (IARC) and adapted by other reviews similar to this study. Categories for level of evidence consisted of sufficient, limited, inadequate, and lack of association. The level of evidence categorization was conducted separately for children (7–18 years), adults, and older adults (over 50).

Of the thirteen studies included in this review, six focused on children. Four of these investigated the association between the school or residential surrounding greenness and school performance, cognitive development, or attentional capacity. While all four reported a beneficial association between green space exposures and these outcomes, only one study was rated as being of good quality.

The adult studies were all considered to be of poor quality, yet they consistently suggested a positive association between green space exposure and cognition. For older adults, two were of fair quality and two of good quality. The results between studies, however, were inconsistent.

While the evidence on the association between green spaces and cognition is inadequate, it does suggest that exposure to greenness might positively influence cognitive development in childhood and cognitive function in adulthood. The authors recommend further and more rigorous research to investigate the association.