WEDNESDAY, Nov. 1, 2006 (HealthDay News) -- Exercise can reduce the risk of developing a more severe form of age-related eye trouble by 70 percent, researchers say.
Age-related macular degeneration (AMD) is a condition in which the light-sensitive cells in the macula at the back of the eye stop working. There are two types of AMD, dry and wet. Wet AMD is more highly linked to serious vision loss.
"We found that people who were more physically active had a reduced risk of developing late-stage AMD," said study author Michael Knudtson, a biostatistician in the department of ophthalmology and visual sciences at the University of Wisconsin's School of Medicine and Public Health.
"This is just an association," Knudtson cautioned. It's not clear whether this association is causal or coincidental, he noted.
The report was published in the Oct. 31 online issue of the British Journal of Ophthalmology.
Starting in 1988, Knudtson and colleagues collected data on nearly 3,900 men and women, aged 43 to 86, in Beaver Dam, Wis. The patients underwent eye exams and were asked about the amount of exercise they got. They were then tracked every five years for 15 years.
The researchers found that one in four of the individuals maintained an active lifestyle, and almost one in four climbed more than six flights of stairs a day. About one in eight walked more than 12 blocks a day.
Knudtson's group found that people with an active lifestyle were 70 percent less likely to develop the more serious wet AMD, compared with those who had a sedentary lifestyle. In addition, people who walked regularly were 30 percent less likely to develop wet AMD, they found.
Knudtson noted that other factors, such as diet, may also explain the findings. Yet physical activity is known to reduce inflammation, which is thought to play a part in AMD.
People who are physically active are also likely to be "biologically younger" than those with a sedentary lifestyle, which could also be important, since AMD is associated with aging, the researchers said.
Knudtson was cautious in interpreting the findings. Exercise is a good thing, he said. "But we don't want people to exercise and then get upset that they [still] get this disease," he said. "We can't prove in any way, shape or form that there is a causal relationship," he added.
One expert believes the findings need to be replicated before the relationship between exercise and AMD is proven.
"Exercise doesn't seem to affect your risk of getting AMD," said Dr. Marco Zarbin, professor and chairman of the Institute of Ophthalmology and Visual Science at New Jersey Medical School. "It seems to affect your risk of getting a particular complication of it."
Zarbin said that if the finding is confirmed in other studies, that would be important, however.
"It's the second behavioral modification, after not smoking, that I know of that would reduce your risk of getting the wet form of the disease," he said.
There's more on AMD at the U.S. National Eye Institute.