Many studies have shown that people living in greener neighborhoods have several health benefits, including lower levels of stress and cardiovascular disease. But new research indicates that exposure to parks, trees and other green spaces can slow the rates at which our cells age.
The study, published in Science of the Total Environment, found that people who lived in neighborhoods with more green space had longer telomeres, which are associated with longer lives and slower ageing.
Telomeres are structures that sit on the ends of each cell’s 46 chromosomes, like the plastic caps on shoelaces, and keep DNA from unraveling. The longer a cell’s telomeres, the more times it can replicate. When telomeres become so short that cells can’t divide, the cells die.
“Research is now showing that where we live, what we are exposed to, how much we exercise, what we eat, each of these can impact the speed of telomeres degrading and again our ageing process,” said Aaron Hipp, a professor of parks, recreation and tourism management at North Carolina State and a co-author of the study. “A longer telomere is usually a younger telomere, or a more protective, helpful telomere. It is protecting that cell from the ageing process.”
Green space promotes physical activity and community interaction, which are both associated with better health outcomes. Neighborhoods with plenty of trees and greenery are also often cooler, more resistant to flooding and have lower rates of air pollution.
However, Hipp noted, participants who lived in green neighborhoods that were also plagued by pollution and segregation did not have longer telomeres than similar communities with less greenery. “Green space [still] matters,” he said. “It just shows how important it is that we get to a level playing field first, so that people have the time and space to go out and enjoy green spaces.”
Hipp and his colleagues looked at the medical records (that included measures of telomere lengths from biological samples) and survey responses from more than 7,800 people who participated in a national Centers for Disease Control and Prevention survey conducted between 1999 and 2002. The researchers connected that information with census data to estimate the amount of green space in each person’s neighborhood. They found that a 5% increase in a neighborhood’s green space was associated with a 1% reduction in the ageing of cells. “The more green the area, the slower the cell ageing,” said Hipp.
Scott Ogletree, a lecturer in landscape and wellbeing at the University of Edinburgh and the report’s lead author, said that green spaces had little impact on telomere length when participants lived in low-income or segregated areas, raising new questions about the relationship between human health and the environment. “It does seem that the neighborhood context” of pollution and segregation “might be washing out any benefit we see from the green space on this particular aspect of people’s health.”
Hipp said that the study only accounted for where participants were living at the time of their physical examinations. “There’s all sorts of interactions with green spaces, and you do them at different [ages],” he said. Exposure to green spaces in childhood may have a different impact on development than it would during middle age.
Peter James, an environmental epidemiologist at Harvard who was not involved with the study said the report was novel in looking at telomeres instead of other measures of health. “We generally find green spaces associated with better health outcomes,” said James. “And this is using telomere length, which is a unique kind of biomarker of ageing.”