Living in areas with more greenery can enhance cognitive function

Summary: Living near green spaces improves processing speed, cognitive function and attention, in addition to improving mental health, researchers report.

Source: Boston University

Cognitive function in middle age is a strong predictor of whether a person may develop dementia later in life.

Now, a new study led by a Boston University School of Public Health (BUSPH) researcher has found that more greenery in residential areas may help improve cognition function in middle-aged women and that this association could be explained by a reduction in depression, which is also a risk factor for dementia.

Published in the magazine JAMA network openedthe study found that exposure to greenery around a person’s home and surrounding neighborhood could improve processing speed and attention, as well as boost overall cognitive function.

The results also showed that reduced depression may help explain the association between greenery and cognition, supporting previous research that has linked exposure to parks, community gardens and other greenery with improved mental health.

“Some of the main ways nature can improve health is by helping people recover from psychological stress and by encouraging people to socialize outdoors with friends, both of which promote mental health,” says Dr. Marcia Pescador Jimenez, lead of the study and corresponding author, and assistant professor of epidemiology at BUSPH.

“This study is one of the few to provide evidence that green space may benefit cognitive function in old age. Our findings suggest that green space should be explored as a potential population-level approach to improve cognitive function.”

For the study, Pescador Jimenez and colleagues from BUSPH, Harvard TH Chan School of Public Health, Brigham and Women Hospital, Harvard Medical School and Rush Medical College estimated green space in homes using a satellite-based metric called the Normalized Difference Vegetation Index (NDVI). ).

They measured psychomotor speed, attention, learning and working memory in 13,594 women, averaging 61 years of age, and primarily whites, from 2014 to 2016.

The women participated in the Nurses’ Health Study II, the second of three studies that are among the largest studies of risk factors for chronic disease in American women.

Adjusted for age, race and socioeconomic status of individual and neighborhood, the researchers found that exposure to green space was associated with psychomotor speed and attention, but not with learning or working memory.

In addition to depression, the researchers also examined the possible role of air pollution and physical activity in explaining the association between green space and cognitive function, and were surprised to find only evidence of depression as a mediating factor.

“We theorize that depression may be an important mechanism by which green space may slow cognitive decline, especially in women, but our research is ongoing to better understand these mechanisms,” says Pescador Jimenez.

The study, published in the journal JAMA Network Open, found that exposure to greenery around a person’s home and surrounding neighborhood could improve processing speed and attention and boost overall cognitive function. Image is in the public domain

“Based on these results, clinicians and public health agencies should consider exposure to green space as a potential factor to reduce depression and thus boost cognition. Policy makers and urban planners should focus on adding more green space into everyday life to improve cognitive function.”

While the study shows evidence of this association, the green space metric the researchers used to measure green space exposure does not distinguish between specific types of vegetation. In a new project, Pescador Jimenez will apply deep learning algorithms to Google Street View images to better understand which specific elements of greenery, such as trees or grass, may be driving health.

The researchers also hope that their study will be replicated in other racial/ethnic populations and that associations with cognitive decline over longer periods of time will be assessed.

“The distribution of greenery in cities is not uniform,” says Pescador Jimenez. “Increasing daily access to vegetation for vulnerable groups in urban cities is a critical next step to achieve health equity.”

About this research news on cognition and green spaces

Writer: Jillian McKoy
Source: Boston University
Contact: Jillian McKoy – Boston University
Image: The image is in the public domain

Original research: Open access.
“Residential green space and cognitive function in a large cohort of middle-aged women” by Marcia Pescador Jimenez et al. JAMA network opened


Abstract

Residential green space and cognitive function in a large cohort of middle-aged women

Interest

Green space can slow cognitive decline by supporting physical activity, psychological recovery, or reducing exposure to air pollution. However, existing studies on the association of green space with cognitive decline are limited.

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Objectively

To investigate whether residential green space was associated with cognitive function in middle-aged women.

Design, setting and participants

As of 1989, the Nurses’ Health Study II enrolled 116,429 female nurses ages 25 to 42 living in the US. In 2014 to 2016, 40 082 women were invited to complete an online cognitive battery. This cohort study analyzed women who had data on both green space exposure and cognitive measures. The data analysis was performed from June to October 2021.

Exposures

Residential exposure to green space was assessed using the Normalized Difference Vegetation Index, a satellite-derived indicator of the amount of ground vegetation. Landsat satellite data on 270 m and 1230 m buffers around each participant’s residential addresses in 2013 were used.

Main results and measures

In 2014 to 2016, cognitive function was measured using a self-managed online battery, the Cogstate Brief Battery, consisting of 4 tasks measuring psychomotor speed, attention, learning and working memory; 3 composite scores were created, summing the mean of all tasks, psychomotor speed/attention and learning/working memory. In addition, the study evaluated possible mediators, including air pollution, depression and physical activity.

Results

The analytical sample included 13 594 women, of whom 13 293 (98%) were white. The mean (SD) age was 61.2 (4.6) years. In models adjusted for age at assessment, race, childhood, adulthood, and neighborhood socioeconomic status, green space was associated with higher global Cogstate composite scores (mean difference per IQR in green space, 0.05; 95% CI, 0.02 to 0.07), and psychomotor speed/attention (mean difference in score, 0.05 standard units; 95% CI, 0.02 to 0.08). This difference in scores is similar to the difference seen in the data in women with a 1-year age difference. In contrast, there was no association between green space and learning/working memory (mean difference 0.0300; 95% CI -0.0003 to 0.0500).

Conclusions and relevance

These findings suggest that increasing residential green space may be associated with modest benefits in cognition in middle-aged women.

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