Effect of Body Mass Index on the Disease Activity of Patients With Rheumatoid Arthritis in a Gender-Specific Manner and the Association of Respective Serum C-Reactive Protein Levels With the Body’s Inflammatory Status

Background Current literature evaluating the effect of high body mass index (BMI) on the disease activity of patients with rheumatoid arthritis (RA) is mixed as some studies have shown a positive, linear relationship between BMI and disease activity while others have demonstrated an inverse correlation. Through this study, we have expanded the effect of BMI on disease activity in patients with RA. We have further expanded on whether BMI influences the disease activity depending on the gender being studied. Finally, we have studied whether there is a correlation between high BMI values and rising C-reactive protein (CRP) levels. Methodology This cross-sectional study was conducted at the Outpatient Clinical Department of Buffalo Rheumatology. The study was ethically approved by the Catholic Health Institutional Review Board. A total number of 451 patients' clinical data was selected based on inclusion/exclusion criteria. The patients were divided into different BMI categories based on the guidelines of national obesity education initiative of the national heart, lung, and blood Institute. The following clinical parameters were studied: BMI, serum CRP level, and disease activity through routine assessment of patient index data questionnaire 3 (RAPID3). The minimum sample size (n = 358) was calculated via the world health organization sample size calculator. All data were entered and analyzed through Statistical Package for the Social Sciences (SPSS), version 16.0 (IBM Corp., Armonk, NY). Results Our study sample included 98 males and 353 females (22% and 78%, respectively). Collective data for both the genders showed significantly increased disease activity in RA patients with high BMI values (p = 0.04). When the data sets were categorized according to the two genders, it was noted that the aforementioned results remain significant for the females only (p = 0.02 for females and p = 0.57 for males). At all BMI values, mean RAPID3 scoring remained significantly higher for females as opposed to their male counterparts (p = 0.006). Mean serum CRP levels increased linearly with increasing BMI (p < 0.001); however, for the underweight patient population, mean CRP levels were the highest as compared to normal weight, overweight, moderately obese, and severely obese patients. Conclusion We conclude that the association between the BMI and the severity of disease remains elusive. High BMI values increase the risk of a pro-inflammatory state of the body due to higher serum CRP levels. Estimating the clinically significant benefit of this theory would require a large-scale clinical trial that would highlight the role of losing weight in improving the patients' quality of life, pain control, and mortality.