Greenery near home linked to 20% lower dementia risk

Within 100 meters of their front door, a little more greenery went hand in hand with a markedly lower risk of dementia. That is the finding of a new study from Stockholm University and the Karolinska Institute, published in the journal Alzheimer's & Dementia. The team followed 2,993 people aged 60 and over for 16 years, and 477 of them developed dementia.

The method is simple to describe. Each year, the researchers measured how much vegetation lay within 100, 250 and 500 meters of each home, using satellite images and mapping software. They then compared that greenery with repeated assessments of participants' cognitive health. The result: residents with more greenery within 100 meters had a 20% lower risk of developing dementia over time. The effect was strongest for the closest greenery and weaker for vegetation farther away, and it was more pronounced among women. The analysis took into account age, education, socioeconomic circumstances, lifestyle, air pollution, traffic noise and proximity to water.

Why might greenery matter? The study does not test this, but the authors point to several possible pathways. Natural environments can support psychological restoration, reduce stress and improve well-being. The team's earlier work, they note, links more greenery near home with better sleep, better mental health, higher life satisfaction and lower use of antidepressant medication. Green spaces can also encourage time outdoors, walking and cycling, and contact with neighbors. Trees and vegetation can reduce traffic noise, air pollution and heat in cities.

The limits matter as much as the number. This is an observational study: it finds an association, and it cannot show that greenery itself prevents dementia. The participants were older adults in Stockholm, so the results may not transfer directly to other cities or populations. A 20% difference in risk is a statistical comparison across groups, not a promise for any individual street or building.

For city planners, residents and developers, the practical consequence is that the green space around housing deserves a place in health planning. The authors say that protecting existing trees, courtyards, gardens and street vegetation should come first, and that new green areas should be accessible and usable for people with different needs and abilities. The study sets no timetable for this, and it does not say how quickly such changes would show up in dementia rates. What it does provide is a measurable reason to treat the trees outside the window as a public-health asset.