Background Obesity has been proposed as a risk factor to develop rheumatoid arthritis (RA) and it has been associated with a worse response to several disease modifying anti-rheumatic drugs (DMARDs).
Objectives To study the differences in baseline characteristics according to the body mass index (BMI) of patients in the PEARL (Princesa Early Arthritis Register Longitudinal) study.
Methods A total of 432 patients (69.1% female) of the PEARL cohort were included for this study. The register protocol comprises the collection of sociodemographic, disease-related and treatment data in five visits (baseline, 6, 12, 24 and 60 months). The local ethics and clinical research committee approved the protocol and all patients sign an informed consent prior to their inclusion. For this study it was analyzed the baseline visit data from the 304 (70.37%) patients that met ACR 1987 criteria for RA after 2 years of follow-up, as well as those considered undifferentiated arthritis (UA) since other diagnoses were excluded. The WHO definition for low, normal weight, overweight and obesity (BMI <18.5, 18.5–25, 25–30 or ≥30 kg/m2 respectively) was applied. ACPA (anticitrullinated peptide antibodies) were assessed by enzyme immunoassay (CCP2 Eurodiagnostica). HLA-DRB1 genotype was determined in 219 patients using specific HLADRB1 typing kits (Dynal RELI SSO). The presence of shared epitope (SE) was determined based on this genotyping. The statistical analysis was performed by using Stata 12.1. Chi-Square and Kruskal-Wallis tests were used for the bivariate analysis. A multivariate logistic regression was performed to determine which factors may be related to ACPA positivity, including BMI, age, sex, smoking habit, number of SE alleles and study level as independent variables.
Results Patients were 54.9 years old [44.2–67.5] (median [p25-p75]); disease duration was 5.3 months [3–8.4]. Table 1 shows the main variables significantly associated to BMI. In addition, we observed less ACPA positivity with increasing BMI (57% low weight vs. 43% in obese [p =0.08]), as well as a lower frequency of SE in patients with a higher BMI. The multivariate analysis confirmed that being smoker (ever or current) and carrying SE alleles is associated with the presence of ACPA. Adjusted by these variables, overweight and obesity were associated with lower probability of suffering an ACPA positive disease (OR 0.49, p=0.027 and OR 0.39, p=0.019 respectively).
Conclusions In our early arthritis register, patients with a higher BMI have predominantly ACPA negative disease, a more intense perception of pain and higher disability. These findings should be validated in other populations.
Disclosure of Interest None declared