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reference
Jimenez MP, Elliott EG, DeVille NV, et al. Residential green space and cognitive function in a large cohort of middle-aged women.JAMA Network Open. 2022;5(4):e229306. doi:10.1001/jamanetworkopen.2022.9306
Study objective
To investigate whether exposure to residential green space is associated with cognitive function in middle-aged women
Key to take away
Residing in an area with more green spaces was associated with better cognitive function in middle-aged nurses and should be further investigated as a potential population-level approach to improving cognitive function.
design
Prospective, observational cohort study
Participant
The cohort used in this study is part of the ongoing Nurses’ Health Study II (NHS II).1From 1989, NHS II recruited female nurses aged 25 to 42 years at the time of enrollment (N=116,429).
Between 2014 and 2016, researchers invited 40,082 NHS II participants to take part in the current study, of which 14,151 completed the self-administered cognitive assessment (Cogstate Brief Battery).
The total sample at the time of analysis (2021) was 13,594 (average age 61.2 years).
All study participants lived in the United States and researchers matched for socioeconomic status; 98% of participants were white.
Evaluated study parameters
The Cogstate Brief Battery is a self-administered test that includes four tasks and is intended to serve as a sensitive indicator of early cognitive deficits. Using this validated test, researchers calculated three composite scores:
- Ein psychomotorischer Geschwindigkeits-/Aufmerksamkeitswert
- Ein Lern-/Arbeitsgedächtnis-Score
- Eine Gesamtkognitionsbewertung
Additionally, data from the Normalized Difference Vegetation Index, which assesses green spaces using satellite imagery, was used to determine each participant's residential green space.
Primary outcome
The study looked at participants' scores on the Cogstate Brief Battery, a computer-based cognitive assessment tool that measures cognition.
Key findings
This study found that increasing green space is associated with higher scores on overall cognition and psychomotor speed/attention. However, there was no difference in learning or working memory.
An interquartile range (IQR) increase in green space exposure within a 270 m (886 ft) buffer zone was associated with higher scores for the combination of psychomotor speed and attention (β, 0.04; 95% CI, 0.02 to 0.07) and overall cognition (β, 0.04; 95% CI, 0.01 to 0.06). Adjusting for individual socioeconomic status in childhood and adulthood did not significantly change the results. These associations were still positive when the buffer zone was changed to 1,230 m (3/4one mile) (β, 0.04; 95% CI, 0.02 to 0.07) and (β, 0.04; 95% CI, 0.02 to 0.06).
The association between green space exposure and learning/working memory composition was positive but not statistically significant when using the 230 m or 1,230 m buffer zones (β, 0.03; 95% CI, −0.00 to 0.05) and (β, 0.02; 95% CI, −0.01 to 0.04).
transparency
The study was supported by a grant from the National Institutes of Health to Dr. Jimenez, Dr. Weuve and Dr. James financed. Dr. Weuve reported receiving personal fees from the Alzheimer’s Association and personal fees from the Health Effects Institute outside of this work.
Implications and limitations for practice
Human contact with nature as a green space and the associated effects have become increasingly interesting for researchers. Perhaps the consideration that nature itself is the basis for the human experience and can therefore be expected to influence the human body in a variety of ways is rightly compelling at a time when 55% of the world's population lives in urban areas and by 2050 68% of the world's population is expected to live in urban areas.2Researchers are studying the importance of contact with green spaces and its connection to neurological health, as access to and contact with nature and wild areas may become less accessible to a growing global population that increasingly lives in urban areas.
Over the past few decades, a growing body of data has emerged demonstrating numerous positive neurological associations with exposure to green spaces, including its effects on children's cognitive abilities.3.4recovery time after surgical events,5Dementia,6mental health,7and more. When working with patients who have problems with cognition, mental health, etc., doctors may rightly consider asking patients about access to nature and time spent there, and depending on the answer, encouraging them to spend more time in nature.
It should be noted that the Normalized Difference Vegetation Index (NDVI), although valuable as a research tool to inform green space within the study parameters, presents its own challenges. Researchers recently reported that it "may not be able to fully characterize the human experience of exposure to trees and plants because scenes with the same normalized vegetation index difference value may appear different to the human eye."8Although a powerful tool, the NDVI cannot capture the full reality of study participants' experiences of and contact with nature as a green space.9For example, city dwellers might intentionally seek opportunities for green space, which would bias the results.
Follow-up studies should examine the effects of actual behaviors and time spent in nature. Additionally, this study aims to help inform urban planners who are able to influence the amount of green space in cities and neighborhoods as populations in these areas increase.
Finally, this study is limited by the limited patient population, as essentially only middle-aged white nurses are studied. This study may also be of limited relevance to individual practitioners as it was not intended to determine whether habitual exposure to green spaces improves cognition. It just shows the effect of staying closer to green spaces, over which individual practitioners have little influence.