In the city, parks and green spaces help to reduce temperatures and promote biodiversity, but they also help to slow down the ageing of cells: according to research published yesterday, Wednesday, in the journal Science Advances, people living near green islands are on average two and a half years younger biologically than others.
«Living near greenery helps keep us younger than our actual age,» explained Kiezu Kim, lead author of the study, a postdoctoral medical researcher at Northwestern University.
«We believe our discovery will have important implications for urban planning in terms of expanding green space, promoting public health and reducing health inequalities,» he added.
The link between being green and better cardiovascular health and lower mortality rates has already been identified. The researchers thought that physical exercise and social interaction in parks played a role in this direction. But until now it was not clear that the parks themselves slow down cellular ageing.
Inequalities
Kim and her colleagues followed more than 900 people, black and white, in four American cities (Birmingham, Chicago, Minneapolis and Oakland) over 20 years, from 1986 to 2006.
Using satellite imagery, the team measured the distance between participants' homes and green spaces. They also tested blood samples taken from participants in the 15th and 20th years of the study to determine their biological age.
The researchers then built scientific models to assess the results and took into account various variables that could affect them, such as education, income, whether they are smokers or not...
They observed that people whose homes were surrounded by 30% of green space within five kilometres were on average 2.5 years younger biologically than those who were surrounded by 20% of green space.
However, the benefits were not the same for everyone.
Blacks living near green were only one year younger than their actual age, while whites were three years younger.
«Other factors such as stress, the quality of green spaces and various social factors may influence the benefits,» Kim explained, adding that these differences should be examined by other research.
For example, people living in deprived neighbourhoods avoid hanging out in the parks there, as they are often used for illegal activities. As a result, their health benefits are less.
Future scientists may look at the link between green spaces and specific health effects on people, Kim noted. How greenery delays aging is not yet clear, she explained, adding that we just know there is a link between greenery and youth.
