Body Mass Index and the Risk of Rheumatoid Arthritis

A Systematic Review and Dose-response Meta-analysis

Baodong Qin; Min Yang; Haitao Fu; Ning Ma; Tingting Wei; Qingqin Tang; Zhide Hu; Yan Liang; Zaixing Yang; Renqian Zhong

Disclosures

Arthritis Res Ther. 2015;17(86) 

In This Article

Abstract and Introduction

Abstract

Introduction The evidence from published studies on the association between obesity and rheumatoid arthritis has been contradictory. To clarify the association between obesity and rheumatoid arthritis, we conducted a systematic review and dose-response meta-analysis to assess the relationship between body mass index and rheumatoid arthritis risk.

Methods A systematic literature search of PubMed and Embase (up to 12 July 2014) was performed to identify all eligible published reports. The pooled relative risk results with corresponding 95% confidence intervals of rheumatoid arthritis development were estimated using a random-effects model.

Results Eleven eligible related citations fulfilled the inclusion criteria and were included in the study. Compared with individuals with a body mass index under 30, obese individuals showed an association with a significantly increased risk of rheumatoid arthritis (relative risk = 1.25, 95% confidence interval: 1.07 to 1.45, P heterogeneity <0.01, I2 = 63%). Compared to normal weight subjects, the pooled relative risks for rheumatoid arthritis were 1.31 (1.12 to 1.53) and 1.15 (1.03 to 1.29) for the categories of obese and overweight, respectively. In the dose-response analysis, there was evidence of a nonlinear association (P nonlinear = 0.005) and the estimated summary relative risk for a 5-unit increment was 1.03 (95% confidence interval: 1.01 to 1.05, P heterogeneity = 0.001, I2 = 70.0%).

Conclusions An increase in body mass index can contribute to a higher risk for rheumatoid arthritis development. However, the finding also highlights the need for research on the association between body mass index and rheumatoid arthritis risk with adjustment for more confounding factors.

Introduction

Rheumatoid arthritis (RA) is the most common autoimmune disease, affecting approximately 0.5 to 1% of the adult population worldwide, and it is characterized by diffuse synovial inflammation and destruction.[1–3] It primarily affects women, with a female to male ratio from about 2:1 to 3:1.[1] Although the etiology and pathogenic mechanism underlying the development of RA remain unclear, the combination of a susceptible genetic background interplaying with environmental factors has been considered to be associated with the development of this complex disorder.[4] It has been reported that there are several risk factors contributing to the initiation and promotion of this complex disorder, such as age, gender, hormonal levels, alcohol, cigarette smoking, socioeconomic status, and dietary habits.[5–8]

Obesity is a major health issue affecting many people. For example, about two thirds of adults and one third of children in the USA are obese.[9] Obesity has contributed to increased morbidity and mortality, and people who are overweight or obese are at increased risk of several diseases. Although body mass index (BMI) cannot measure the percentage of body fat and accurately reflect obesity, it is also considered to be a useful indicator for obesity. In a previous study, the association of obesity with RA was demonstrated,[10] but another study examining the association of BMI with RA risk yielded different and controversial results.[11] Several prior studies have observed a positive relationship between BMI and increased risk of developing RA, suggesting obesity is an important and modifiable risk factor for RA.[10,12] Conversely, some studies did not identify this association.[11,13,14]

Due to these conflicting results, we conducted a systematic review and meta-analysis of the available literature to quantitatively assess the effect of BMI on RA development. In addition, the exact shape of the dose-response relationship between BMI and RA risk has not been clearly defined; therefore the other aim of this study was to clarify the dose-response relationship between BMI and RA risk.

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