Now, a study of nearly 62 million Medicare beneficiaries suggests that nature may also help protect against the risk of developing certain neurodegenerative diseases.
The results revealed that older adults who lived in a ZIP code with more green space had a lower rate of hospitalization for Parkinson’s disease, Alzheimer’s disease, and related dementias such as vascular dementia and Lewy body dementia.
Blue space — bodies of water such as lakes, rivers, and oceans — and the amount of land dedicated to parks within a given zip code were also associated with lower hospitalizations for Parkinson’s disease, but not for Parkinson’s disease. Alzheimer’s and associated dementias.
Nature can reduce stress levels
Why this remains unclear, but leading theories suggest that nature reduces our body’s stress levels while increasing our ability to concentrate. Proximity to forests, parks, and other green outdoor common spaces can also encourage physical activity and provide opportunities to connect with other people.
Regular exercise and social interaction can help prevent Alzheimer’s disease and general cognitive decline, while chronic stress has been linked to an increased risk of dementia. Exercise can also reduce the risk of developing Parkinson’s disease.
“We also know that in general, air pollution and noise levels are lower in greener environments,” said study author Jochem Klompmaker, Harvard postdoctoral researcher TH Chan. School of Public Health. “Some of these mechanisms may be linked to Alzheimer’s disease and Parkinson’s disease.”
The protective associations of green spaces with hospitalization declined after adjusting for air pollution, but remained significant, implying that other factors are at play. The findings were published by JAMA Network Open in December .
“This is not the first study to show this association between green spaces” and dementia/Parkinson’s disease, “but one of its great strengths is the very large population studied,” said Anjum Hajat, professor associate in epidemiology at the University of Washington, who was not involved in the research. “No other study has been so important.”
Klompmaker and colleagues looked at ZIP codes and hospital admissions for all fee-for-service Medicare beneficiaries age 65 and older who lived in the contiguous United States from 2000 to 2016.
Health Benefits of Green Spaces, Blue Spaces, and Park Coverage
To assess exposure to natural environments, they analyzed the amount of green space, blue space, and park coverage for each beneficiary’s residential zip code. Green space was defined by the Normalized Difference Vegetation Index (NDVI), a measure of the greenness of a plot of land calculated using satellite imagery.
An NDVI of 1, for example, signifies the presence of dense green vegetation such as forest, whereas urbanized areas with a scarcity of trees would score closer to 0. “The NDVI captures green vegetation”, Klompmaker said. “It could be the grass in your garden, the trees in the street, or even the crops on the farmland.”
The researchers also used satellite imagery to collect blue space values for the water, while the park’s percentage coverage was based on the US Geological Survey’s protected areas database. Hospitalizations included Medicare beneficiaries who had a primary or secondary discharge diagnosis of Parkinson’s disease, Alzheimer’s disease, or related dementias.
The results confirm what other smaller studies have observed in terms of neurodegenerative nature and disorders.
A 2022 study of four US cities found that a high number of residential green spaces was associated with a reduced risk of dementia in older adults. A 2021 review of 22 studies suggested positive associations between green spaces and measures of brain health linked to Alzheimer’s disease.
DuWayne Heupel, 69, lives in Colorado Springs, a nature lover’s paradise with more than 9,000 acres of parkland and 500 acres of trails. “We have a lot of green space in Colorado Springs,” Heupel said. “It definitely helps my health, especially my mental outlook.”
And in a 2020 study, residents of Vancouver, British Columbia, living near roads had a higher incidence of Parkinson’s disease, Alzheimer’s disease, and related dementias, but greenery seemed to have a protective effect.
“Based on the available evidence, we can say that the more contact with nature, the better,” said Payam Dadvand, associate research professor at the Barcelona Institute for Global Health, whose own research focuses on the effects of air pollution and green spaces on human health. His 2018 analysis of 6,506 older people in the UK found slower cognitive decline over a ten-year follow-up period for those who lived in areas with more green space.
Researchers have hypothesized that exposure to nature provides health benefits by:
- Reduce damage — reduce exposure to air pollution, noise, and heat.
- Psychological restoration – stress reduction and improved ability to concentrate.
- Facilitation of healthy behaviors — encouraging physical activity and social cohesion.
Bill Furey, 61, of Placentia, California, remembers the exact moment he witnessed the healing power of nature. At age 12, he and his classmates, along with their middle school science teacher, went on a hike to the bottom of the Grand Canyon.
Furey’s father had died of pancreatic cancer a year earlier and his mother thought the trip would be good for him.
“It was the first time I felt at peace since my father passed away, and it was the start of my wandering the woods to find healing for the soul,” said Furey, who now runs the Heritage Hiking Club (HHC), based in Orange County. , California. “I’m certainly no scientist, but something magical happens when you wake up with dirt under your boots.”
He met some of his best friends through the hiking group, and several members even got married, Furey said.
Josie Robarge of Banning, Calif., started walking and running regularly outdoors just over a decade ago. Now, at 56, she walks at least twice a week with other members of social groups such as HHC.
“These are the people you choose to live with – cheerleaders, motivators, and friends who will put a wall around you if you have to use the restrooms in Zion National Park and can’t come back to the Visitor Center !” Robarge said.
If your neighborhood doesn’t have an abundance of nature, visit a forest reserve or hiking trail, experts said.
Growing evidence that green spaces are good for health should also lead national and local leaders to increase such spaces in urban areas and develop new natural spaces, Dadvand said.
“Getting out into nature is good for your health, not just in terms of dementia and Parkinson’s disease, but we can assume that many different health parameters will be improved by being outdoors and more connected to nature,” Hajat said.
