Research shows exposure to green space around one’s home and surrounding neighborhood may improve overall cognitive function in middle-aged women. Key TakeawaysA new study found that exposure to green space could improve processing speed and attention in middle-aged women.Reduce rates of depression may help explain this link between green space and cognition.The study builds on previous
Green space—trees, grass, flowers, forests, parks, or gardens—is more than just “nature.” It’s important to humans’ very existence and wellbeing. And new research shows that’s particularly true for middle-aged adults.
“There is extensive literature on the beneficial aspects of green space on health,” Marcia Pescador Jimenez, PhD, assistant professor of epidemiology at Boston University, told Verywell. But she said there isn’t much research about its effects on cognition in older groups of people.
“We wanted to close that gap,” she added.
Along with colleagues from Boston University, Harvard, Brigham and Women’s Hospital, and Rush Medical College, Pescador Jimenez analyzed residential green space and cognitive measures for thousands of middle-aged women. They found that green space exposure was associated with faster thinking skills and better ability to concentrate.
“Our findings suggest that green space should be investigated as a potential population-level approach to improve cognitive functions,” Pescador Jimenez said. “This means that our results can inform urban planners and policy makers on how to create cities and interventions that support healthy aging.”
The study was published in JAMA Network Open in late April.
If you or someone you know is worrying about their mental wellbeing, but access to green areas is a challenge, Pescador Jimenez said even looking at images of green spaces can be restorative. Same goes for having indoor plants, looking at trees though the windows, or getting involved in community gardens.
To carry out the study, Pescador Jimenez and colleagues needed to estimate two things: participants’ cognitive abilities and the green space around their houses.
To analyze cognitive function, researchers measured data from 13,594 women with an average age of 61, of whom 98% were White, between 2014 and 2016. The data was collected as part of the Nurses’ Health Study II, one of the largest investigations into the risk factors for chronic diseases among U.S. women. Specifically, researchers looked at psychomotor speed, attention, learning, and working memory.
Psychomotor speed refers to speed of thinking measured through action. One measure for this called the trail making test, which asks participants to connect numbers and/or letters in ascending order as quickly as possible.
To measure green space in the vicinity of study participants, researchers used a satellite image-based metric called the Normalized Difference Vegetation Index (NDVI) to assess whether the areas around the participants’ homes contained live green vegetation.
After adjusting the data for differentials like age, race, and socioeconomic status, the researchers found that green space exposure was associated with enhanced psychomotor speed and attention compared to controls, but not learning or working memory.
To explain the link between green space and improved attention, the researchers ran something called a mediation analysis to look for any other related mechanisms. For example, green space is often associated with reduced air pollution, as well as increased physical activity, which can in turn lower risk of depression.
The analysis showed that depression, a known risk factor for dementia, was the only significant mediating factor. This means that enhanced cognitive function associated with living near green space may be at least partially explained by lowered depression.
To better understand this potential link with depression, Pescador Jimenez says to think about what green space can mean to individuals and a community.
“Green space can promote cognitive health by increasing opportunities for physical activity and social connection,” she said. It also offers a relief from stress associated with noise and air pollution. All of these factors may connect back to the mediating effect of depression identified in the study.
This study’s limitations mostly revolve around technology and representation. For example, Pescador Jimenez said that the NDVI, while well-established and standardized across studies, cannot distinguish between trees, grass, crops, or other types of vegetation. She explains this is fundamental for policy relevance.
Plus, the most direct contact people get with greenery is best represented by “ground-based measures,” which capture what a person sees from their perspective. “Our team is working on novel metrics of green space using deep learning algorithms combined with Street View Imagery to classify detailed types of vegetation from a ground-based view as participants experience them,” Pescador Jimenez said. “Stay tuned!”
The researchers hope that their study will be replicated among more diverse populations.
Activists and researchers have been advocating for more equitable access to green space in the U.S. for years. Yet social and environmental forces still stand in the way.
For example, a 2019 analysis demonstrated access to urban vegetation “is generally associated with traditional markers of privilege in U.S. cities,” such as being White, having more years of formal schooling, and higher income.
“Increasing everyday access to vegetation across vulnerable groups in urban cities is a crucial next step to achieve health equity,” Pescador Jimenez in a press release.
At the same time, other researchers warn that growing green space can inadvertently bolster gentrification. According to a research paper published in the journal Landscape and Urban Planning, over time, this process can displace “the very residents the green space strategies were designed to benefit.” Because of this, the authors say green interventions should be supported by anti-gentrification policies, such as affordable housing and rent stabilization programs.
If you don’t live particularly close to green space, it can seem impossible to incorporate it into your life. But Pescador Jimenez said that even just looking at or watching images or videos of green spaces can help with psychological restoration.
“Having indoor plants or looking at trees through the windows would probably help,” she said.Study: Exposure to Greenery May Support Aging Minds View Story