Living in greener neighborhoods during midlife may slow cognitive decline

Research has shown that approx 40% of dementia could be prevented or delayed worldwide by addressing modifiable risk factors associated with the condition, especially during midlife.

A new study led by a researcher from Boston University School of Public Health (BUSPH) provides deeper insight into how one risk factor – living near green spaces such as parks and trees – in midlife can yield cognitive benefits later in life. age.

Published in the news Environmental health perspectivesThe study found that living in areas with more green space during midlife can slow a person’s annual rate of cognitive decline by about eight months. This association was stronger among people living in low socio-economic status (SES) and densely populated neighborhoods.

This association was also observed in people with the APOE-ɛ4 gene, a variant of the APOE gene that is a major risk factor for Alzheimer’s disease. APOE-ɛ4 carriers exposed to more greenery had a threefold rate of slower cognitive decline, compared to people without the gene, which is an important research development as there are currently no known ways in which carriers of this gene can reduce their risk of developing the gene. can reduce the development of dementia. .

Exposure to greenness has previously been linked to better cognitive functioning, but this new study includes a much larger study group and a longer observation period than previous analyses. It is also the first study to investigate how different environmental characteristics may influence the relationship between greenness and cognition in carriers of the APOE-ɛ4 gene.

Given that Alzheimer’s disease and related cases of dementia can develop up to 20 years before recognizable symptoms appear, it is critical to identify which population groups are most susceptible to these conditions and take protective measures as early as possible life can be implemented to thwart or prevent these diseases. slow cognitive impairment.

“Our results are important because they shed light on the cognitive benefits of increasing exposure to green space at the population level, especially among vulnerable subgroups of the population, such as carriers of the APOE-ɛ4 gene,” said study leader and corresponding author Dr . Marcia Pescador Jimenez, assistant professor of epidemiology at BUSPH.

To investigate the link between greenery in homes and cognitive functioning and decline, Dr. Pescador Jimenez and colleagues from Rush Medical College, Rush Alzheimer’s Disease Center, and Harvard TH Chan School of Public Health used data from the Nurses’ Health Study (NHS), a prospective study that began in 1976 and is one of the largest studies of the risk factors for chronic diseases among American women.

The team focused on 16,962 nurses aged 70 or over who took part in an NHS sub-study that started between 1995 and 2001 and lasted through 2008. Participants were assessed for their cognitive functioning through telephone surveys, and the researchers used a satellite image-based measurement to measure the green level around the living areas of participants. They assessed exposure to greenness up to nine years prior to the first cognitive test, and the total cognitive assessment included five cognitive tests administered up to four times over an average of six years.

After adjusting for age and socioeconomic factors, higher average exposure to greenery during midlife was linked to higher levels of cognitive functioning and to slower cognitive decline, based on global cognition scores but not on verbal memory.

Importantly, this association was stronger for participants living in low SES and densely populated neighborhoods, suggesting that efforts to increase green spaces in disadvantaged areas could help reduce socioeconomic inequality among these populations.

“Our finding for participants living in neighborhoods with lower socio-economic status is consistent with the theory of equigenic environments, which suggests that greenness may be important to reduce socio-economic health inequalities,” says Dr. Pescador Jimenez.

The study also examined the role of mental health in the relationship between exposure to greenness in midlife and cognition. While previous research has suggested that limited exposure to greenery in midlife may reduce cognitive functioning through depression, the new data extends this link by suggesting that greenness over time may be associated with cognitive decline through mental health .

“The findings highlight the importance of prioritizing the preservation and creation of green spaces, especially in low-SES neighborhoods, as a means of promoting cognitive health later in life,” says Dr. Pescador Jimenez.