April 28, 2011 -- Adults with arthritis are more likely than those without arthritis to be obese, according to a new government study.
''The frequency of obesity is 54% higher among people with arthritis compared to those without,'' says Jennifer Hootman, PhD, an epidemiologist with the CDC.
She is the co-author of the report, published in the CDC's Morbidity and Mortality Weekly Report.
"That was higher than I thought [it would be]," she tells WebMD. "I thought it would be 30% or 40%."
An estimated 72.5 million U.S. adults ages 20 and older are obese; 50 million have arthritis, according to the report.
The CDC researchers wanted to evaluate how many people with doctor-diagnosed arthritis were obese compared to people who do not have arthritis. They analyzed data from the Behavioral Risk Factor Surveillance System (BRFSS) for the years 2003 to 2009.
The BRFSS is a telephone survey conducted annually with adults from all 50 states, the District of Columbia, Guam, Puerto Rico, and the U.S. Virgin Islands.
Data on arthritis and obesity are collected in odd-number years.
Survey takers asked the participants if they had any diagnosis of arthritis. They asked about osteoarthritis and rheumatoid arthritis. Osteoarthritis, also called ''wear-and-tear'' arthritis, is more common than rheumatoid arthritis, which involves chronic joint inflammation. They also asked about gout, lupus, and fibromyalgia.
For each of the four years analyzed, the prevalence of obesity for the 50 states and D.C. was higher among adults with arthritis than those without.
In 2003, 33.2% of those with arthritis from all 50 states and D.C. were obese, while 21.4% of those without arthritis were.
By 2009, 35.2% of those with arthritis were obese, while 23.6% of those without were.
The number of states that had 30% or more of its residents with arthritis classified as obese rose from 38 in 2003 (including D.C.) to 48 in 2009.
The rise in obesity among those with arthritis increased enough to be considered significant from a statistics point of view in Puerto Rico and 14 states.