Large study finds incidence decreases with amount of exercise.
Here's a benefit-of-running angle you don't hear all that often: This sport might lower your risk for developing cataracts, or clouding of the eye lens.
Writing in Medicine & Science in Sports & Exercise, Paul Williams, Ph.D., describes the latest finding from his large, long-term National Runners Health Study. In 2009, Williams had reported that cataract risk decreased significantly among men runners with increased mileage. For this study, he broadened the participant pool to include women runners, as well as regular walkers of both sexes.
Williams found that his latest data analysis supported his earlier finding. In more than 32,000 runners and 14,000 walkers, the more they walked or ran, the less likely they were to be diagnosed with cataracts during the study's six-year follow-up period. The risk reduction was equal between men and women.
Like other exercise-science types, Williams describes activity level in terms of METs (for "metabolic equivalent"), which gives activities a value in relation to how much energy you expend doing that activity compared to sitting still. Walking at a good pace, for example, is usually given a MET value of around 3, while running at 10:00 mile pace is usually given a MET value of around 10 (that is, it takes roughly 10 times as much energy to run at that pace as it does to sit on your couch thinking about running at that pace).
Williams found that, when overall energy expenditure was the same, walking and running provided similar risk reductions for developing cataracts. And again, Williams found that more energy expenditure was associated with less risk of developing cataracts.
The runners in the study, however, had less risk of developing cataracts than the walkers for the simple reason that it's easier to amass a given amount of METs running than walking. That being the case, the most active runners in the study were the ones with the least incidence of cataracts. Compared to what would be expected for people of their age, those whose energy expenditure from running was the equivalent of averaging more than five miles a day had a 41% lower risk of developing cataracts.
Williams says that several mechanisms might explain why the more active people had the lowest risk of developing cataracts. One possibility is that many lifestyle-related conditions, such as Type 2 diabetes, hypertension and obesity, have been linked to developing cataracts, and being highly active can forestall those conditions.
By Scott Douglas
By Scott Douglas
Published
May 22, 2013
