A new study reports that overweight and obese people with juvenile idiopathic arthritis (JIA) are more likely to have inflamed lower limb joints. The study also suggests that higher body weight may have a negative effect on disease course and response to treatment; however, the data is not totally clear and further studies are necessary to test these associations.
The study, “The Influence of Overweight and Obesity on Treatment Response in Juvenile Idiopathic Arthritis,” was published in the journal Frontiers in Pharmacology.
Being overweight may exacerbate inflammatory diseases such as JIA; in addition to causing more mechanical stress on the body, fat tissue can release inflammatory molecules. In rheumatoid arthritis — which is similar to but not the same as JIA — being overweight has been linked to poorer responses to treatment and worse disease progression, but the effect of body weight on these factors in JIA hasn’t been thoroughly assessed.
To shed light on this association, researchers reviewed the records of 110 JIA patients who were treated at the Meyer Children’s Hospital in Florence, Italy. These patients were divided into two groups: those with a body mass index (BMI) between the fifth and 85th percentile (80 people, deemed the healthy weight group) and those with a BMI above the 85th percentile (30 people, the overweight/obese group).
The researchers noticed that at baseline (before treatment), patients in the heavier group had, on average, significantly more active (inflamed) joints in their lower limbs, possibly indicative of increased inflammation and/or mechanical stress in this group.
Other measures of inflammation, such as levels of the inflammatory marker C-reactive protein, were not significantly different between the groups — that is, the researchers couldn’t rule out the possibility that this observed difference was simply the result of chance — but the heavier group trended toward higher levels.
When treated with conventional disease-modifying anti-arheumatic drugs (DMARDs), 69 of the patients achieved remission. Although the rate was slightly lower in the overweight/obese group than in the healthy weight group (83.58% and 98.87%), this difference was not statistically significant.
Of those 69 people, 35 relapsed after going into remission. The relapse rate was slightly higher in the overweight/obese group (15.79% vs. 13.37%), but again, this difference was not statistically significant.
This same trend was also observed among patients treated with anti-tumor necrosis factor (TNF) biologic therapies; those in the heavier group tended towards poorer responses, but the results didn’t reach statistical significance.
Importantly, this study included a relatively small number of patients, and it’s often difficult to rule out chance in a small sample unless the effect is particularly dramatic. So, it is possible — even likely — that the lack of statistical significance observed in this study is mostly a result of the small sample size limiting conclusions that can be drawn. Additional studies that include more patients may help to clarify whether or how body weight affects treatment response in JIA patients.
The researchers stated, “Despite the fact that our data do not identify obesity as an independent risk factor for JIA, they suggest a negative influence on disease activity at baseline and an unfavorable impact on the therapeutic response to conventional DMADs and anti-TNF drugs.”
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