(AP) -- A surprising jump in the number of Americans hobbled by arthritis may be due to obesity, health experts said Thursday.
About 22 percent of U.S. adults have been told by a doctor that they have arthritis, the Centers for Disease Control and Prevention reported. The statistic comes from national telephone polling of tens of thousands of adults in 2007 through 2009.
That translates to nearly 50 million people with the joint disease. It's also roughly the same percentage with arthritis as reported in a 2003-2005 study.
But there was a significant jump in adults who said their joint pain or other arthritis symptoms limited their usual activities, to 9.4 percent from 8.3 percent. That means more than 21 million adults have trouble climbing stairs, dressing, gardening or doing other things, up from less than 19 million only a few years before, the CDC researchers estimated.
That jump was "more than we would have expected," said Dr. John Klippel, president of the Atlanta-based Arthritis Foundation.
Klippel said the increase probably was due mainly to baby boomers, who are at an age when they are more likely to suffer osteoarthritis, the most common form of arthritis. It breaks down cartilage and causes pain and joint stiffness.
He added that a complicating factor is high rates of baby boomers who are overweight and obese. Extra weight puts more pressure on arthritic joints, making the problem worse, he said.
The percentage of people who were hobbled was more than twice as high in obese people as those who were normal weight or were underweight, the CDC researchers found. Obesity can lead to or worsen osteoarthritis in the knees, the researchers wrote.
The study is published in a CDC publication, Morbidity and Mortality Weekly Report.
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