The health benefits of spending time in the great outdoors

According to a study published last month in the Archives of Ophthalmology, nearsightedness, called myopia, has increased in the U.S. by 66% since the early 1970s. And the intensity of the disorder has also increased—that is, the prevalence of people with moderate cases of myopia has nearly doubled since the 70s.

Susan Vitale, an epidemiologist at the National Eye Institute and the study’s co-author, partly attributes this prevalence to near-work, such as watching television or playing video games, as she explained in a radio segment on NPR.

In the same segment, Don Mutti of the College of Optometry at the Ohio State University suggested the rise was due to growing up primarily indoors, in addition to near-work and genetics. During a 20-year study, Mutti found that nearsightedness and time spent outdoors were directly related:

If you have two nearsighted parents and you engage in a low level of outdoor activity, your chances of becoming myopic by the eighth grade are about 60 percent. If children engaged in over 14 hours per week of outdoor activity, their chances of becoming nearsighted were now only about 20 percent. So it was quite a dramatic reduction in the risk of becoming myopic.

In a Wired article, Jane Gwiazda, a psychologist at the New England College of Optometry in Boston, also linked the lack of outdoor time with myopia: “Some people think that more distance viewing sends a signal to the eye to stop growing.” In other words, looking at the horizon in a vast landscape might calibrate our eyes for distance-viewing.

She also says that natural light boosts vitamin D, which could help regulate eye growth, and stimulates dopamine production, a chemical known, among other things, for inhibiting eye growth. Those who suffer from myopia have elongated eyes; vitamin D and dopamine, then, could help prevent the eyes from changing shape. Dopamine is also linked to mood elevation, sleep regulation and increased attention and focus.

Our vision, therefore, is not the only thing being impacted by less time outdoors. In a study published last year in Current Directions in Psychological Science, people working in an environment with access to windows (and, therefore, natural light) felt significantly calmer than those who worked in a windowless office. And even people who worked in an office with photos of the outside simulated on a television screen had about the same feelings of tranquility as those who had nothing on their walls.

In addition, another study found that being surrounded by nature prompted people to have better focus and attention than when they were in a crowded city environment. As the study’s co-author Marc Berman explains, urban areas are filled with stimuli—like cars, pedestrians, flashing lights—which demand a great deal of our attention. Being outside in the open, slower setting of a natural environment, therefore, allows our brains to just relax.

Photo Credit: © Randall K. Roberts

Vitale, S., Sperduto, R., & Ferris, F. (2009). Increased Prevalence of Myopia in the United States Between 1971-1972 and 1999-2004 Archives of Ophthalmology, 127 (12), 1632-1639 DOI: 10.1001/archophthalmol.2009.303

Kahn, P., Severson, R., & Ruckert, J. (2009). The Human Relation With Nature and Technological Nature Current Directions in Psychological Science, 18 (1), 37-42 DOI: 10.1111/j.1467-8721.2009.01602.x

Berman, M., Jonides, J., & Kaplan, S. (2008). The Cognitive Benefits of Interacting With Nature Psychological Science, 19 (12), 1207-1212 DOI: 10.1111/j.1467-9280.2008.02225.x

Author: Katie Kline

Moderator of EcoTone and ESA's communications officer.

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