Background/Purpose: Obesity is a common problem with patients who have rheumatoid arthritis (RA). Adipose tissue has been shown to produce cytokines that are proinflammatory. The measurement of Body Mass Index (BMI) is a proxy for determining the amount of adipose tissue present in an individual. The impact of BMI on disease activity measures in RA have been contradictory, and, in fact, studies have shown that a high BMI is protective, as defined by x-ray changes for patients with early onset RA. The objective of this trial is to determine whether obesity and BMI are positively correlated with diverse disease activity measures (DAMs) in longstanding RA.

Methods: Patients at a community based rheumatology clinic undergo DAM assessments on a routine basis as part of the implementation of a treat to target (T2T) strategy. These assessments include the disease activity score in 28 joints (DAS28CRP), the power Doppler joint count (UPD), and the multibiomarker disease activity test (MBDA), as well as several other commonly assessed DAMs. The UPD includes scoring at six dorsal wrist and six dorsal MCP sites. The average duration of RA in patients at this clinic is > 10 years. Also, as currently mandated by the authorities, BMI and other vital signs are obtained on a regular basis. Correlations were determined by Pearson’s coefficients, and categorical data was compared by T tests. Patients were categorized as underweight (BMI < 18), normal weight (BMI > =18 and <25), overweight (BMI >=25 and <30), and obese (BMI >= 30).

Results: Table 1 BMI and Comparisons with Diverse Disease Activity Measures

There were only two patients in the underweight category, and that category was not included in this analysis.

Conclusion: BMI positively correlates with, and shows significant increases in weight categories for several important measures of disease activity in patients with longstanding RA. Though the DAS28CRP, MBDA, and UPD generally correlate significantly in this clinic (r= > 0.500), in this study, UPD was the only one of these measures that did not correlate with BMI (r = 0.090). One possible explanation is that power Doppler signals are very dependent on the distance of the probe from the site of the signal. The UPD method utilized includes assessments of the dorsal wrist at six out of twelve sites. Subcutaneous adipose tissue in overweight patients perhaps blunted the signals. Of interest, Leptin was significantly correlated with BMI and showed significant increases with weight categories. Leptin is produced by adipose tissue and is thought to be proinflammatory. Excess Leptin production might be contributory to the effects of BMI on RA disease activity. BMI is positively correlated with several important DAMs in patients with longstanding RA. Rheumatologists should significantly increase their efforts and resources to address and manage obesity in our RA patients.  

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/body-mass-index-is-positively-correlated-with-diverse-disease-activity-measures-in-longstanding-rheumatoid-arthritis/