[Correlation analysis between body mass index and clinical characteristics of rheumatoid arthritis]

To analyze the clinical features of overweight and obese rheumatoid arthritis (RA)patients, and the relationship between body mass index (BMI) and disease characteristics.

The demographic data, extra-articular manifestations, comorbidities, and disease activity of RA patients admitted to the Rheumatology and Immunology Department of Peking University Third Hospital from January 2015 to December 2020 were collected, and the above characteristics of overweight and obese RA patients were retrospectively analyzed. According to the WHO, BMI≥30 kg/m² referred to obese individuals, 25≤BMI < 30 kg/m² referred to overweight individuals, 18.5≤BMI < 25 kg/m² referred to normal individuals, BMI < 18.5 kg/m² referred to reduced body mass individuals. t test was used for the quantitative data in accordance with normal distribution. Wilcoxon rank sum test was used for the quantitative data of non-normal distribution. The qualitative data were analyzed by chi square test. But while 1≤theoretical frequency < 5, Chi square test of corrected four grid table was used. And Fisher exact probability method was used when theoretical frequency < 1. Analyzing whether overweight or obesity was associated with comorbidities using Logistic regression adjusted confounding factors.

A total of 481 RA patients were included in this study, with an average BMI value of (23.28±3.75) kg/m².Of the patients, 31 cases (6.5%) were with BMI < 18.5 kg/m², 309 cases (64.2%) with 18.5≤ BMI < 25 kg/m², amounting to 340 cases (70.7%). There were 119 overweight individuals (25≤ BMI < 30 kg/m², 24.7%) and 22 obese individuals (BMI≥30 kg/m², 4.6%), totaling 141 (29.3%).The proportion of the overweight and obese RA patients suffering from hypertension (57.4% vs. 39.1%, P < 0.001), diabetes (25.5% vs. 15.0%, P=0.006), hyperlipidemia (22.7% vs. 10.9%, P=0.001), fatty liver (28.4% vs. 7.4%, P < 0.001), osteoarthritis (39.0% vs. 29.4%, P=0.040) was significantly higher, and the proportion of the patients with osteoporosis(59.6% vs. 70.9%, P=0.016) and anemia (36.2% vs. 55.6%, P < 0.001) was significantly lower. However, there was no difference between the two groups in coronary heart disease (5.7% vs. 7.6%, P=0.442), cerebrovascular disease (6.4% vs. 8.8%, P=0.372) and peripheral atherosclerosis (9.2% vs. 7.6%, P=0.565).The median C-reactive protein (CRP, 1.52 mg/dL vs. 2.35 mg/dL, P=0.008), median erythrocyte sedimentation rate (ESR, 34.0 mm/h vs. 50.0 mm/h, P=0.003), pain visual simulation score (VAS) (3.66±3.08 vs. 4.40±2.85, P=0.011), and 28 joint disease activity scores (DAS-28, 5.05±1.60 vs. 5.45±1.52, P=0.010) in the overweight and obese RA group were all lower than those in the normal and reduced weight groups. Multivariate regression analysis showed that overweight and obesity was an independent risk factor for hypertension, diabetes, hyperlipidemia and fatty liver, and had protective effects on osteoporosis and anemia.

In RA patients, RA disease activity is lower in overweight and obesity patients. Overweight and obesity is associated with hypertension, diabetes and hyperlipidemia, but not with cardiovascular and cerebrovascular diseases.