THURSDAY, Oct. 15, 2009 (HealthDay News) -- The closer you live to nature, the healthier you're likely to be.
For instance, people who live within 1 kilometer of a park or wooded area experience less anxiety and depression, Dutch researchers report.
The findings put concrete numbers on a concept that many health experts had assumed to be true.
"It's nice to see that it shows that, that the closer humans are to the natural environment, that seems to have a healthy influence," said Dr. David Rakel, director of integrative medicine and assistant professor of family medicine at the University of Wisconsin School of Medicine and Public Health.
One previous study had noted fewer health inequalities between rich and poor people in areas with lots of green space, and other studies have echoed these health benefits. But much of this research had relied on people's perceptions of their physical and mental health.
This new objective look at the matter involved scouring medical records of 345,143 people in Holland, assessing health status for 24 conditions, including cardiovascular, respiratory and neurological diseases. This information was then correlated with how much green space was located within 1 kilometer and 3 kilometers of a person's postal code.
People living in more urban environments had a higher prevalence of 15 of the 24 conditions, with the relationship strongest for anxiety disorder and depression.
In areas with only 10 percent of green space, about 2.6 percent of people experienced anxiety disorders, compared to 1.8 percent of people in areas with 90 percent green space. The disparity was evident for depression as well -- 3.2 percent of people living in more urbanized areas had depression versus 2.4 percent of those in more rural areas.
The health benefits were evident only when the green acres were within a kilometer, not at the 3 kilometer perimeter, except for anxiety disorders, gastrointestinal digestive disorders and so-called medically unexplained physical symptoms, the researchers said.
Children and poor people suffered disproportionately from lack of green acres, the researchers found.
The study findings were published online Thursday in the Journal of Epidemiology and Community Health.
Any number of factors could account for the benefits of green space, experts said.
More natural sunlight, for instance, has been linked with a lower incidence of Seasonal Affective Disorder (SAD) and other benefits.
"If patients in hospitals have direct exposure to sunlight through a window or natural sunlight, hospital stays are shorter and patients have less complications," Rakel said. "That's been well-established.
More light also means more vitamin D in the skin, which has been found to elevate mood and improve muscle strength, he added.
And fresh air, obviously, has a benefit as well, as do the exercise opportunities that come with more open space.
But much of the relief may come from the simple ability to de-stress.
"If we're in a busy street with more technology and artificial things, we're going to be multi-tasking more, which prevents us from focusing on one thing," Rakel said. "In this day and age, we really need some sort of centering practice. We need to get our mind out of its own stories and focus on something that's pure. Nature is a beautiful example of that -- it's the way things were meant to be."
This study has "implications not only for city planning but also for indoor design and architecture," said Richard Ryan, professor of psychology, psychiatry and education at the University of Rochester Medical Center. But the benefit is proportional to how much people pay attention to nature, he said.
"If they're in their heads and not paying attention, it doesn't do them much good," said Ryan, co-author of a recent study report that people who are exposed to natural elements are more socially oriented, more generous and value community more. Another experiment he was involved in found that people who spent time outdoors had more vitality and energy.
More green space may also be a way for whole communities to become healthier.
"As health-care costs spiral out of control, it behooves us to think about our green space in terms of preventive health care," said Dr. Kathryn J. Kotrla, associate dean and chair of psychiatry and behavioral science at Texas A&M Health Science Center College of Medicine Round Rock campus. "This highlights very clearly that our Western notion of body-mind duality is entirely false. The study shows that we are a whole organism, and when we get healthy that means our body and our mind get healthy."
The World Health Organization has more on how environments can affect health.