"That's a substantial burden of pain," Smith said.
But in people with arthritis, 60 percent reported troubling pain in the last month of life, compared with 26 percent of those without arthritis, according to the study.
Pain did not differ significantly among people with other conditions, such as cancer or heart disease, the study found.
"This is an important study that confirms what we have learned from smaller, more select studies, and it quantifies pain in the last months of life," said Dr. M.C. Reid, director of the Cornell-Columbia Translational Research Institute of Pain in Later Life, in New York City.
"I think that one of the important findings to emerge is that the prevalence of clinically significant pain was separate from a terminal diagnosis," Reid said. "People with advanced illness are reporting significant levels of pain, but the mechanisms behind that pain aren't yet well understood."
Both Smith and Reid said the study's findings show its important for all doctors to be able to effectively treat pain because it's so prevalent across all conditions.
"It's really the responsibility of all physicians to attend to pain, not just pain doctors," Smith said. "Pain may not be why they're seeing their physician -- for example, someone with heart disease might see a cardiologist most often -- but the cardiologist should ask about pain."
The American Pain Foundation has more about end-of-life pain management.
SOURCES: Alexander K. Smith, M.D., M.P.H., assistant professor, medicine, University of California, San Francisco, and staff physician, San Francisco VA Medical Center, San Francisco; M.C. Reid, M.D., Ph.D., director, Cornell-Columbia Translational Research Institute on Pain in Later Life, New York City; Nov. 2, 2010, Annals
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