Obesity may protect joints in rheumatoid arthritis

NEW YORK (Reuters Health) - Among people with rheumatoid arthritis, joint damage appears to be more severe for those with a normal body mass index (BMI) than for those who are obese, a German research team reports.

This apparent protective effect of obesity, however, is seen only in people who test positive for so-called rheumatoid factor in their blood, Dr. Gisela Westhoff and associates report in the medical journal Arthritis and Rheumatism.

Westhoff, of the German Rheumatism Research Centre in Berlin, and her colleagues evaluated 767 patients who had had rheumatoid arthritis for less than two years. Forty percent had a normal BMI, 41 percent were overweight and 19 percent were obese.

The average score on a standard rating scale for joint damage seen on x-rays among the patients with a normal BMI was 9.7 in those who tested positive for rheumatoid factor and 4.6 among those who tested negative. There was no statistical difference in corresponding scores among obese patients -- 4.1 versus 3.4, respectively.

Nonetheless, despite their findings, Westhoff's group emphasizes that "obesity still is, as seen in this study, an important source of increased pain, increased functional disability, impaired health, and impaired quality of life in patients with rheumatoid arthritis."

SOURCE: Arthritis and Rheumatism, November 2007.