Living near green spaces linked to 21% lower dementia risk

A 16-year study of nearly 3,000 older adults in Sweden found that greater greenery within 100 metres of their homes was associated with a lower risk of developing dementia.

In Short

• Researchers tracked 2,993 dementia-free older adults, with 477 later diagnosed
• Vegetation exposure was assessed across 100, 250 and 500-metre residential zones
• Women recorded a hazard ratio of 0.69, indicating a stronger association

Living close to parks, trees and other green spaces may be associated with a lower risk of developing dementia in older adults, according to a Swedish study that followed nearly 3,000 people for 16 years.

The research, published in Alzheimer’s & Dementia, found that older adults with more greenery within 100 metres of their homes had a lower incidence of dementia. The association was stronger among women than men.

Researchers followed 2,993 participants who did not have dementia at the beginning of the study. During the 16-year follow-up period, 477 participants developed clinically diagnosed dementia.

To assess exposure to greenery, the researchers measured vegetation around participants’ homes within three distances: 100 metres, 250 metres and 500 metres. They then examined the relationship between the amount of greenery and the likelihood of developing dementia.

The findings showed that greater green space within 100 metres of a person's home was associated with a 21% lower hazard of dementia. The researchers reported a hazard ratio of 0.79, with a 95% confidence interval ranging from 0.64 to 0.96.

A hazard ratio compares the rate at which an outcome occurs between groups over time. In this study, the result suggests that people with greater nearby greenery experienced a lower rate of dementia during the follow-up period.

However, the association became weaker when researchers examined larger areas around homes. This suggests that the immediate residential environment may be particularly relevant, although further research is needed to understand why.

WOMEN SHOWED A STRONGER ASSOCIATION

The researchers also examined whether the relationship between greenery and dementia differed according to sex.

The association appeared stronger among women. Greater residential greenery was linked to a 31% lower dementia hazard among women, with a hazard ratio of 0.69.

Among men, the estimated hazard ratio was 0.93, with a 95% confidence interval ranging from 0.71 to 1.24. This result did not establish a statistically significant association between nearby greenery and dementia risk in men.

These findings suggest that the relationship between residential green space and brain health may differ across population groups. However, the study does not explain why the association was stronger among women.

Researchers also examined other factors, including air pollution, traffic noise, the presence of blue spaces such as water bodies, age and the APOE 4 genetic variant, which is associated with Alzheimer's disease risk.

HOW GREEN SPACES MAY SUPPORT BRAIN HEALTH

The study adds to growing interest in how the environment in which people live may influence their health as they age.

Green spaces may offer several benefits that could indirectly support brain health. Trees and vegetation can help reduce exposure to certain air pollutants, while green surroundings may also help buffer traffic noise. Both air pollution and prolonged noise exposure have been investigated for their possible links with cognitive health.

Access to parks and green neighbourhoods may also encourage people to walk, exercise and spend time outdoors. Regular physical activity is important for cardiovascular health, and maintaining good heart and blood vessel health is relevant to brain function.

Spending time in natural surroundings may also help reduce stress and support mental wellbeing. Parks and community green spaces can provide opportunities for social interaction, which may help older adults remain connected to others.

However, these are possible explanations rather than mechanisms proven by this particular study. The researchers examined the relationship between residential greenery and dementia incidence, rather than establishing that each of these benefits directly explained the findings.

MORE RESEARCH IS NEEDED

The researchers concluded that greater residential greenery may be associated with a lower incidence of dementia among older adults, particularly women.

The study's long follow-up period and detailed assessment of green space strengthen the evidence on the relationship between residential environments and brain health. However, its observational design means it cannot prove cause and effect.

Dementia is a complex condition influenced by multiple factors, including age, genetics, cardiovascular health and lifestyle. Green spaces should therefore be viewed as one possible component of a broader approach to healthy ageing, rather than a guaranteed way to prevent the condition.

Further studies are needed to establish whether the relationship holds in other populations and whether changes to urban green spaces can lead to measurable improvements in cognitive health.

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