To examine secular trends in demographics, clinical manifestations, and comorbidity on first presentation of rheumatoid arthritis (RA) prior to disease-modifying antirheumatic drug treatment.
A total of 2,701 patients were recruited over 25 years to 2 UK-based RA inception cohorts: the Early Rheumatoid Arthritis Study (9 centers; 1986-2001) and the Early Rheumatoid Arthritis Network (23 centers; 2002-2012). Trends in demographic and baseline clinical/laboratory and radiographic variables and comorbidities were estimated using mixed-effects models, including random effects for recruitment center.
Age at onset increased from 53.2 to 57.7 years in 1990 and 2010, respectively (2.6 months/year; 95% confidence interval [95% CI] 1.2, 4.1). Sex ratio, the proportion living in deprived areas, and smoking status were unchanged (P > 0.05) and there were no changes in the proportion seropositive or erosive at baseline (P > 0.05). After controlling for treatment at the time of assessment, erythrocyte sedimentation rate decreased and hemoglobin increased over time (P > 0.05); however, the Health Assessment Questionnaire (HAQ), the Disease Activity Score (DAS), the DAS in 28 joints, and joint counts were unchanged (P > 0.05). The overall prevalence of comorbidity increased from 29.0% in 1990 to 50.7% in 2010, mainly due to cardiovascular and non-cardiac vascular conditions, including hypertension. There was a significant increase in body mass index (0.15 units/year; 95% CI 0.11, 0.18), resulting in an increase in the prevalence of obesity from 13.3% in 1990 to 33.6% in 2010.
Age at onset and comorbidity burden, especially obesity, have increased at RA presentation over 25 years, reflecting wider demographic trends at the population level. In contrast, there were no accompanying changes in disease severity assessed by composite markers of disease activity, radiographic erosions, seropositivity, or HAQ at presentation. Treatment strategies in early RA should take greater account of the impact of comorbidity on outcomes.