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Clearing Up Some Confusion: Exercise and Macular Degeneration

May 31, 2018

If you happened to read the December 14, 2017 article in the New York Times on macular degeneration and found yourself feeling worried about your eyesight and anxious to exercise, you’re not alone.

The Times article generated controversy when it reported the findings of a Korean observational study on vigorous exercise and macular degeneration that left many scientifically savvy readers calling for stricter statistical review.

The Korean study, conducted using subjective self-reports, suggested that vigorous exercise may increase the risk for age-related macular degeneration, a condition responsible for vision loss in more than 10 million Americans – more than those affected by cataracts and glaucoma combined.

Korean researchers relied on questionnaires to assess the physical activity of 211,960 men and women ages 45 to 79 in 2002 and 2003. Following this, they tracked diagnosis for age-related macular degeneration from 2009 to 2013. Macular degeneration, the leading cause of blindness in the elderly, is characterized by a progressive deterioration of the retina.

Vigorous exercise, the study found, was linked with a 54 percent increased risk of macular degeneration in men, though this did not hold true for the female subjects of the study.

The authors explain that “excessive exercise might affect the eye’s choroid, a sensitive vascular membrane that surrounds the retina,” but “epidemiologic studies cannot provide any evidence for the mechanism or pathology.”

One of the more perplexing flaws of the study is that “vigorous exercise” was never clearly defined in the participants’ self-completed questionnaire, leaving their responses highly subjective and uncontrolled for with variance analysis.

In other words, “vigorous exercise” could have been interpreted by participants in dramatically different ways. For one, it may have meant climbing a flight of stairs. For another, it may have meant going on a 30 minute walk. For another, it may have meant an hour of jogging.

The Times article on the study came under fire by readers in the face of multiple better controlled and longer studies demonstrating the benefits of exercise in relation to macular degeneration. 

For example, a study conducted at the University of Wisconsin, Madison, by the Department of Ophthalmology and Visual Sciences concluded that, “Women in the highest quintile compared with those in the lowest quintile for physical activity (in metabolic energy task hours per week) had 54 percent lower odds for early age-related macular degeneration.”

The now famous Beaver Dam Study looked at the relationship between exercise and age-related macular degeneration. 3,874 men and women between the ages of 43-86 years were recruited for this study and followed for fifteen years. The study found that those with an active lifestyle (walking three times or more a week), were 70 percent less likely to develop macular degeneration than those who were mostly sedentary.

Though the Times acknowledged at the end of the article that the authors of the study themselves point out that it does not prove cause and effect, many scientifically trained readers were dismayed by what they viewed as misleading and irresponsible medical journalism.

Specifically, scientifically savvy readers were concerned that the article could potentially render readers unduly wary of one of the few things indisputably linked to good eye health and overall health: regular exercise.

As one reader pointed out, “The article as written is likely to mislead most readers. They see ‘54% increase’ and it sounds dreadful. And yet if you look at the study, it surveyed 211, 960 people and the number of physically active people diagnosed with macular degeneration was 250 while it was 198 in those who were not active. So you get a percentage of 0.24% versus 0.19%. Compare 0.24% to 0.19% and you come up with the 54% increase. And yet, if you look at the total number of people studied, you are talking about a 0.05% difference. Within the uncontrolled conditions of the study, this is statistically insignificant.”

Further, though the Korean study controlled for more than 40 variables, it did not control for smoking, which has been definitively linked with an increased risk in age-related macular degeneration.

In a particularly significant twist, the study itself clearly stated: smoking “was more prevalent among the active than the inactive participants,” leading critical readers to suspect that it was not the controlled-for variable of vigorous exercise that accounted for the increased risk reported in the study but rather the uncontrolled-for variable of smoking. 

Overwhelmingly, both common sense and scientific research point to the benefits of regular exercise in maintaining and preserving eye health and overall health, but if you’re concerned about the state of your vision, especially if you’re over 60, you can buy yourself some peace of mind with an optical exam at OCLI.

As New Jersey’s most reputable, comprehensive vision health provider, OCLI delivers warm, friendly, state-of-the-art treatment for all your eyecare needs, including screenings for age-related macular degeneration. OCLI is easy to reach and there to ensure you feel confident and that your future looks clear.

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