Green neighbourhoods may help stave off dementia

People who live in greener neighbourhoods are protected from the common age-related loss in cognitive function that leads to disorders like dementia, a study has found.

Researchers from Barcelona Institute for Global Health (ISGlobal) in Spain performed a 10-year follow-up of 6,500 people aged 45 to 68 in the UK.

At three different time points during the course of the study, participants completed a series of cognitive tests that assessed their verbal and mathematical reasoning, verbal fluency and short-term memory, as well as the decline in these functions.

Neighbourhood green space for each participant was estimated using satellite images.

"There is evidence that the risk for dementia and cognitive decline can be affected by exposure to urban-related environmental hazards (such as air pollution and noise) and lifestyle (such as stress and sedentary behaviour).'

In contrast, living near green spaces has been proposed to increase physical activity and social support, reduce stress, and mitigate exposure to air pollution and noise.

"Recent evidence has shown cognitive benefits of green space exposure in children, but studies on the possible relations of exposure to green spaces and cognitive decline in older adults are still very scarce and often have inconsistent results," said Carmen de Keijzer, a researcher from ISGlobal.

"Our data show that the decline in the cognitive score after the 10-year follow-up was 4.6 per cent smaller in participants living in greener neighbourhoods," said Keijzer.

"The observed associations were stronger among women, which makes us think that these relations might be modified by gender," he said.

"The proportion of people over 60 years old in the world is expected to nearly double between 2015 and 2050 and the number of dementia cases has been predicted to grow at a similar pace worldwide," said Payam Dadvand, a researcher from ISGlobal.

"Although the differences in cognitive decline observed in our study are modest at individual level, they become much more significant if we consider these findings at population level," said Dadvand.

"If confirmed by future studies, our results may provide an evidence base for implementing targeted interventions aimed at decelerating cognitive decline in older adults residing in urban areas and hence improving their quality of life," he said.