To determine the association of obesity, defined as a body mass index (BMI) ≥30 or ≥28 kg/m(2)  or by waist circumference (WC), with disease activity and severity, as well as its relationship to comorbidities in rheumatoid arthritis (RA).
The study population comprised 1,596 patients with early RA (mean ± SD age 55.6 ± 14.6 years, 67.8% women) who had been included in the Better Anti-Rheumatic Farmacotherapy observational study from 1992-2006. In 2010, data on lifestyle factors and comorbidities were collected through a postal questionnaire, answered by 1,391 patients. Clinical outcomes were the Disease Activity Score in 28 joints, sustained remission, physical function (Health Assessment Questionnaire [HAQ]), and pain and global health assessed on a visual analog scale, as well as predefined comorbidities.
After a mean ± SD of 9.5 ± 3.7 years, the mean ± SD BMI had increased from 25.4 ± 4.2 to 26.0 ± 4.5 kg/m(2)  (P = 0.000). The prevalence of BMI ≥30 kg/m(2)  was 12.9% at baseline and 15.8% at followup. In multivariable regression, BMI and obesity, defined as a BMI ≥30 or ≥28 kg/m(2) , at both inclusion and the time of the survey were independently associated with higher disease activity, fewer patients in sustained remission, higher HAQ score, more pain, and worse general health. Also, BMI and obesity independently conferred to higher odds for being diagnosed with hypertension, diabetes mellitus, and chronic pulmonary disease. Further, BMI and WC were independently associated with angina pectoris/acute myocardial infarction/coronary revascularization. In contrast, none of the examined obesity variables was associated with the prevalence of stroke or transient ischemic attack. Lifestyle changes during the observational period, such as quitting smoking or diet change, had no impact on the outcomes.
Obesity was associated with worse RA disease outcomes and a higher prevalence of comorbidities. Body measurements are recommended to improve prediction of the disease course.