People with impaired vision take 26% fewer steps per day than normal-sighted individuals and are about half as active physically, which could increase their risk of chronic illness, says a report by Maryland researchers in Archives of Ophthalmology. Loss of vision affects mobility and balance, but rehabilitation programs rarelystressphysical exercise, they said.

Physical activity was assessed in 5,722 subjects from a 2003-2006 U.S. health survey, of whom 5,226 had normal vision, 351 needed glasses to see normally, and 145 had low vision that couldn't be corrected to normal. Normal eyesight was defined as 20/40 or better, which is the minimum driving requirement in most states. Activity levels were assessed with an accelerometer worn on the hip for approximately 14.3 hours a day over seven days. All subjects underwent eye examinations.

Individuals with low vision took 5,992 steps per day compared with 9,964 for normal-sighted people and 9,742 for those with glasses. Average daily exercise was 9.3 minutes in low-vision subjects and 23.5 minutes in the other groups. The study is the first to report an association between visual impairment and objectively measured physical activity.

Caveat: Accelerometer readings don't capture upper-body exercise or swimming activities and shouldn't be taken as absolute, researchers said. The study didn't account for the normal age-related physical decline.