People who suffer chronic pain tend to have general physical capabilities similar to those decades older, a new study finds.

Scientists re-examined data from a 2004 study of 18,531 people age 50 and over. As one example, among participants age 50 to 59 who had no chronic pain, 37 percent could jog a mile and 91 percent could walk several blocks with no trouble. Among those with chronic pain, only 9 percent could jog the mile and only half managed the walking task.

"We found that the abilities of those aged 50 to 59 with pain were far more comparable to subjects aged 80 to 89 without pain, of whom 4 percent were able to jog 1 mile and 55 percent were able to walk several blocks, making pain sufferers appear 20 to 30 years older than non-pain sufferers," said study leader Kenneth Covinsky of the Division of Geriatrics at the University of California, San Francisco.

Chronic pain is a huge problem for middle-aged and older adults. In fact 24 percent of the people in the study suffered from moderate to severe pain most of the time. About 75 million U.S. residents endure chronic or recurrent pain, other studies have found. Migraines plague 25 million of us. One in six suffer arthritis.

While pain is poorly understood, many experts now recommend physical exercise to combat many types of chronic pain, in addition to medication in some cases.

"Our study cannot determine whether pain causes disability or whether disability causes pain," Covinsky said. "We think it is likely that both are true and that pain and disability probably can act together in ways that make both problems worsen in a downward spiral."

The findings, announced today, are detailed in the Journal of the American Geriatric Society.

The research suggests pain and disability may often be part of the same underlying process. "Patients may be better served if pain and disability are evaluated and treated jointly rather than treated as separate issues," Covinsky said.