Background: Rheumatoid arthritis (RA) is a complex inflammatory disease that modifies body composition. Although body mass index (BMI) is one of the clinical 48 nutrition tools widely used to assess indirectly nutritional status, it is not able to identify these body alterations. Bioelectrical Vector Analysis (BIVA) is an alternative method to assess hydration and body cell mass of patients with wasting conditions. Objective: To investigate the differences in nutrition status according to BMI groups (normal, overweight and obesity) and BIVA classification (cachectic and non-cachectic) in women with RA. Methods: Women with confirmed diagnosis of RA were included from January 2015 to June 2016. Whole-body bioelectrical impedance was measured using a tetrapolar and mono-frequency equipment. Patients were classified according to BMI as: low body weight (n=6, 2.7%), normal (n=59, 26.3%), overweight (n=88, 39.3%) and obese (n=71, 31.7%), and each 58 group was divided into BIVA groups (cachectic 51.8% and non-cachectic 48.2%). Results: A total of 224 RA patients were included, with mean age 52.7 years and 60 median disease duration of 12 years. Significant differences were found in weight, 61arm circumference, waist, hip, resistance/height, reactance/height and erythrocyte sedimentation rate among all BMI groups. However, serum albumin levels were significantly different between cachectic and non-cachectic patients independently of BMI. In all BMI categories, cachectic groups had lower reactance and phase angle than non-cachectic subjects. Conclusion: RA patients with normal or even high BMI have a significantly lower muscle component. Evaluation of body composition with BIVA in RA patients could be an option for cachexia detection.

Introduction

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by inflammation, joint pain, and destruction of the synovial membranes [1]. Life expectancy of these patients can be reduced by an average of 3 to 18 years and 80% are disabled after 20 years [2, 3]. Metabolic alterations in RA due mainly to the liberation of tumor necrosis factor alpha and interleukin-1 beta can lead to rheumatoid cachexia, which is defined as “the involuntary loss of fat free mass (FFM) with minimal or not weight loss and increase or not of fat mass (FM)” which causes muscular weakness and loss of functional capacity. Also, the mean loss of FFM, present in almost two thirds of patients with RA, is between 13 and 15%. [4]. In clinical nutrition practice, a widely-employed tool used to evaluate body mass and hence nutritional status is the body mass index (BMI). However, its main  limitation is that is not able to identify rheumatoid cachexia alterations such as loss of FFM and gain of FM [5]. Several imaging techniques have been used to analyze body composition in RA patients. Currently, the most useful tool for measuring soft tissue mass and bone mineral density is dual X-ray absorptiometry (DXA) [6, 7]. Nevertheless, DXA is not always accessible and is sensitive to the patient’s hydration status [8] and also is associated with radiation exposure [9]. Therefore, a simple tool for identifying body composition alterations as rheumatoid cachexia in outpatient settings is necessary [10].