Characteristics of hospitalisations for autoimmune rheumatic diseases in Ireland 2015–2023: analysis of hospital in-patient enquiry data

Abstract Introduction The SYNERG-IE research programme aims to address the unmet needs of patients with Sjögren’s disease (SjD) and Sjögren’s associated with additional autoimmune rheumatic diseases (AIRDs), which are chronic, multisystemic conditions that frequently lead to significant morbidity and health service utilization.1,2 Despite their clinical complexity, there is limited population-based evidence describing hospitalisation patterns among patients with AIRDs in Ireland. Understanding these trends is essential to inform service planning, identify changing patterns of disease burden, and optimise inpatient management strategies. Aim To examine trends and characteristics of hospitalisations related to autoimmune rheumatic diseases in Ireland by analysing the Hospital In-patient Enquiry (HIPE) database. Methods Data were obtained from the HIPE database and included all inpatient discharges with AIRDs listed as the principal diagnosis between 2015–2019 and 2022–2023. AIRDs were identified using the International Classification of Diseases (ICD)-10 codes and included Rheumatoid Arthritis (RA, M05/M06), Systemic Lupus Erythematosus (SLE, M32), SjD (M35.0), Systemic Sclerosis (SSc, M34), Myositis (including Polymyositis/Dermatomyositis, M33), and Mixed/Undifferentiated Connective Tissue Diseases (MCTD/UCTD, M35.1/M35.8/M35.9). Analyses focused on temporal trends in hospitalisations, and descriptive statistics were used to summarise patient characteristics, length of stay (mean, standard deviation), admission type, discharge status, and clinical specialty. Comorbidities (excluding AIRDs) were identified from additional diagnosis records to assess their frequency and distribution. Results Overall, 3942 inpatient hospitalisations were recorded, with RA (65.6%) being the commonest coded condition, followed by SLE (14.1%), and SSc (8.9%). Trend analyses showed overall number of hospitalisations per year remained relatively stable, with a decreasing trend in RA, more marked declines in SjD, and a slight upward trend in SSc, SLE, and myositis. Compared to RA, patients with other AIRDs had significantly longer hospitals stays (mean 5.4 vs 10.4 days), with the longest mean duration of admissions for myositis at 16 days. Prolonged hospitalisations (90 days) were more commonly observed in patients with myositis and SjD. Patients with SLE and myositis were significantly more likely to have emergency admissions compared to their counterparts. SjD (24.7%) and SLE (27.7%) patients were significantly less likely to be admitted under a rheumatologist. Nephrology and orthopaedics were common specialties to care for hospitalised SLE (22.1%) and RA (21.9%) patients, respectively. We observed significantly higher rates of neurological admissions in SjD patients in comparison to all other AIRDs (24% vs 1.5%). Conclusion This study used comprehensive, national administrative dataset capturing all hospital discharges in Ireland for AIRDs, providing robust population-level estimates; however, the use of routinely coded data limits clinical detail and may be subject to coding variability. We observed a reduction in RA-related admissions over time potentially due to earlier diagnosis and access to advanced therapies. This was offset by increased rates of admission with SSc, SLE, and myositis, and patients with these AIRDs often required prolonged hospital stay. Access to new therapies for AIRD patients as they become available may improve outcomes. High rates of neurological admission in SjD patients warrant prospective evaluation.