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Public health
Original research
Outdoor green space exposure and brain health measures related to Alzheimer’s disease: a rapid review
  1. Lilah Besser
  1. Institute for Human Health and Disease Intervention, Florida Atlantic University, Boca Raton, Florida, USA
  1. Correspondence to Dr Lilah Besser; lbesser{at}fau.edu

Abstract

Objectives Summarise studies of outdoor green space exposure and brain health measures related to Alzheimer’s disease and related disorders (ADRD), and determine scientific gaps for future research.

Design Rapid review of primary research studies.

Methods and outcomes PubMed, Embase and Web of Science Core Collection were searched for articles meeting the criteria published on/before 13 February 2020. The review excluded papers not in English, focused on transient states (eg, mental fatigue) or not using individual-level measures of brain health (eg, average school test scores). Brain health measures of interest included cognitive function, clinical diagnosis of cognitive impairment/dementia/ADRD and brain biomarkers such as those from MRI, measures typically associated with ADRD risk and disease progression.

Results Twenty-two papers were published from 2012 to 2020, 36% on <18 years old, 32% on 18–64 years old and 59% on ≥65 years old. Sixty-four per cent defined green space based on the Normalised Difference Vegetation Index (‘greenness’/healthy vegetation) and 68% focused on cognitive measures of brain health (eg, memory). Seventeen studies (77%) found green space-brain health associations (14 positive, 4 inverse). Greater greenness/green space was positively associated various cognitive domains in 10 studies and with MRI outcomes (regional brain volumes, cortical thickness, amygdala integrity) in three studies. Greater neighbourhood greenness was associated with lower odds/risk of cognitive impairment/ADRD in some studies but increased odds/risk in others (n=4 studies).

Conclusions Published studies suggest positive green space-brain health associations across the life course, but the methods and cohorts were limited and heterogeneous. Future research using racially/ethnically and geographically diverse cohorts, life course methods and more specific green space and brain health measures (eg, time spent in green spaces, ADRD biomarkers) will strengthen evidence for causal associations.

  • delirium & cognitive disorders
  • old age psychiatry
  • public health
  • preventive medicine
  • dementia

Data availability statement

Data sharing not applicable as no datasets generated and/or analysed for this study. Deidentified data (ie, search results from the databases) are available on request of LB (lbesser@fau.edu). Any reuse or sharing of these data require LB’s approval.

http://creativecommons.org/licenses/by-nc/4.0/

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

http://dx.doi.org/10.1136/bmjopen-2020-043456

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    Data availability statement

    Data sharing not applicable as no datasets generated and/or analysed for this study. Deidentified data (ie, search results from the databases) are available on request of LB (lbesser@fau.edu). Any reuse or sharing of these data require LB’s approval.

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    Footnotes

    • Contributors LB is the sole author of this paper and as such completed all of the work, including data acquisition and interpretation, drafting and revising the paper for intellectual content, final approval of the version to be published, and agreement to be accountable for all aspects of the work.

    • Funding LB is supported by National Institutes of Health/National Institute on Aging award K01AG063895.

    • Competing interests None declared.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.