Abdominal obesity ups risk of rheumatoid arthritis in women

Abdominal obesity appears to contribute to an increased risk of rheumatoid arthritis (RA), particularly seropositive RA, among young and middle-aged women, a study has shown. However, it does not independently contribute to RA risk beyond general obesity.

The investigators followed a total of 50,682 women (1986–2014) in the Nurses’ Health Study (NHS) and 47,597 women (1993–2015) in NHS II without RA at baseline. Then, they obtained waist circumference (WC), body mass index (BMI), health outcomes, and covariate data through biennial questionnaires. Chart review was used to identify incident RA cases and serologic status.

Finally, the investigators used time-varying Cox proportional hazards models to examine the associations of WC and BMI with RA risk. They repeated analyses restricted to those aged ≤55 years.

A total of 844 incident RA cases (527 NHS and 317 NHS II) had been identified over 28 years of follow-up. Women with WC >88 cm (35 in) were at greater risk of RA (hazard ratio [HR], 1.22, 95 percent confidence interval [CI], 1.06–1.41). A similar association was seen for seropositive RA, which was more robust among young and middle-aged women. Further adjustment for BMI eased the association to null.

On the contrary, BMI correlated with RA (BMI ≥30 vs <25 kg/m²: HR, 1.33, 95 percent CI, 1.05–1.68) and seropositive RA, even after adjusting for WC. Just like in WC analyses, this association was more pronounced among young and middle-aged women.

“Being overweight or obese increases RA risk among women, particularly among those diagnosed at a younger age,” the investigators said. “Abdominal obesity may contribute to systemic inflammation more than general obesity.”