Incidence, prevalence and mortality of rheumatoid arthritis in general practice in New Zealand

INTRODUCTION: Rheumatoid arthritis (RA) is a chronic inflammatory condition that affects the joints, skin, eyes, lungs, heart, blood vessels, and nervous system. AIM: This study aims to estimate the incidence and prevalence of RA in New Zealand and compare the mortality of RA patients with the general population. METHODS: Patients with a SNOMED CT code for RA in 2018-2025 were identified from the Pinnacle dataset. The WHO (World Health Organization) age-standardised rate (ASR) of incidence and prevalence of RA were calculated by ethnicity and gender (women and men). The standardised mortality ratio (SMR) was estimated to compare the relative rate of observed deaths in RA patients with the expected deaths in the general population. RESULTS: We identified 3831 RA patients during the study period. The age-standardised incidence of RA was 26.9 (95% CI: 22.8-30.9) per 100,000 population. Women (34.8, 95% CI: 28.3-41.3, per 100,000) had around twice the incidence of RA than men (18.2, 95% CI: 13.5-22.9). The age-standardised prevalence of RA was 417.5 (95% CI: 402.8-432.1) per 100,000 population. The prevalence was 583.0 (95% CI: 558.8-607.2) per 100,000 for women and 237.6 (95% CI: 221.8-253.3) for men. Asians had the highest age-standardised incidence but the lowest age-standardised prevalence among all ethnic groups. The SMR of all the incident RA patients compared to the general population was 1.07 (95% CI: 0.80-1.34). DISCUSSION: The prevalence of RA in general practice aligns with rates observed in secondary care settings. The upward trend in RA prevalence raises concerns about escalating healthcare system burdens, including increased costs and resource demands. The rise in RA prevalence was driven by increasing incidence among Asian populations.