New research provides evidence that some types of natural environments are associated with a decreased risk hospitalization for neurological diseases such as Alzheimer’s disease and Parkinson’s disease. The findings have been published in JAMA Network Open.
“We were interested in the relation between natural environments and hospitalization because there were some indications that natural environments could affect the risk and/or exacerbate symptoms of Alzheimer’s disease and related dementias and Parkinson’s disease,” said study author Jochem O. Klompmaker, a postdoctoral researcher at the Harvard T. H. Chan School of Public Health.
“For example, exposure to natural environments, such as forests, parks, and blue spaces, can help reduce stress, provide settings for physical activity and social interactions, and may reduce exposure to air pollution. Other studies observed protective associations of natural environments with cognitive decline, mental health and stroke.”
The researchers examined data from nearly 62 million Medicare recipients aged 65 years or older who lived in the contiguous United States from January 1, 2000, through December 31, 2016. roughly 7.7 million were hospitalized for Alzheimer’s disease and related dementias, while nearly 1.2 million were hospitalized for Parkinson’s disease.
The researchers used residential zip codes to estimate exposure to natural environments such as parks, waterways, or vegetation such as trees, crops, or grass. They found that living in zip codes with a higher than average amount of vegetation was linked to lower rates of first-time hospitalizations for Alzheimer’s disease. Living near any type of nature was linked to lower rates of first-time hospitalizations for Parkinson’s disease.
“Our findings suggest that exposure to some natural environments may reduce the risk of Alzheimer’s disease and Parkinson’s disease hospitalization among older adults,” Klompmaker told PsyPost. “As life expectancy increases globally, and no cures exist for Alzheimer disease and related dementias or Parkinson’s disease, policy makers may consider interventions of natural environments to prevent hospitalizations.”
Interestingly, the presence of parks appeared to provide the greatest buffer against Parkinson’s disease in low-socioeconomic status neighborhoods, while general vegetation appeared to provide the greatest buffer in mid- and high-socioeconomic status neighborhoods
“We observed stronger protective associations of percentage park cover with Parkinson’s disease hospitalization in low socioeconomic status zip codes,” Klompmaker said. We do not know the exact reason, but think that individuals from low-socioeconomic status neighborhoods tend to use parks more often than other individuals.”
The researchers controlled for factors such as age, sex, and ethnicity. But the study, like all research, includes some caveats.
“A limitation of this study is that we lacked information about the residential address of each beneficiary, therefore, we assessed natural environment at zip code level,” Klompmaker noted. “In addition, no information about the quality and safety of parks, greenness, and blue spaces was available.”
The researchers proposed some pathways that might help explain why natural environments could help to lower the risk of Alzheimer’s disease and Parkinson’s disease hospitalizations. For example, green spaces might reduce exposure to air pollutants, provide stress reduction, give people the opportunity to engage in physical activity, and help to facilitate social interactions. But “further research is needed to study potential pathways underlying the associations,” Klompmaker said.
The study, “Associations of Greenness, Parks, and Blue Space With Neurodegenerative Disease Hospitalizations Among Older US Adults“, was authored by Jochem O. Klompmaker, Francine Laden, Matthew H. E. M. Browning, Francesca Dominici,Marcia P. Jimenez, S. Scott Ogletree, Alessandro Rigolon, Antonella Zanobetti, Jaime E. Hart ,and Peter James.