A total of 315,190 hospitalizations were recorded for RA patients, both in primary and secondary diagnosis, during the period of 2002–2017. Of these admissions, 211,967 were women (67.3%), and 103,199 were men (32.7%). The mean age of the patients was 68.5 ± 13.9 years, corresponding to 68.2 ± 14.5 years in women and 69.1 ± 12.6 years in men (p > 0.05). The median length of hospital stay over the entire study period was 7 days (IQR 3–11 days); the length of stay was significantly higher in 2002 (8 days, IQR 4–13 days) compared to 2017 (6 days, IQR 3–10 days) (p < 0.05). In 2002, the cost of hospitalization for RA patients was 38 million euros, with a median hospitalization cost per admission of 2,314 euros (IQR 2,032–3,417 euros), whereas the total cost was 142 million euros in 2017, with a median hospitalization cost per admission of 4,396 euros (IQR 3,384–5,945 euros) (p < 0.05). The overall cost of hospitalizations for patients with RA in the Spanish Health System was 1.476 million euros during the period of 2002–2017, with a median hospitalization cost per admission of 3,542 euros (IQR 2,646–5,222 euros).
Hospitalization rates by sex, age, year and diagnosis. The hospitalization rate in Spain for RA during the period of 2002–2017 was 43.8 (95% CI: 43.7–44.0) hospitalizations per 100,000 population-years. By sex, the rate of hospitalization was 58.1 (95% CI: 58.0–58.3) per 100,000 population-years in women and 29.1 (95% CI: 29.0–29.3) in men (p < 0.05). When stratified by age, the lowest hospitalization rate corresponded to those under 20 years old: 0.53 (95% CI: 0.49–0.56) per 100,000 population-years, and the highest corresponded to those between 80–90 years old: 219.0 per 100,000 population-years (95% CI: 217.5–220.6) (Table 1). When comparing the annual rate of hospitalization without differentiating whether RA was coded as the main diagnosis or a comorbidity, there was an annual increase in this rate from 31.6 per 100,000 inhabitants in 2002 to 56.3 per 100,000 inhabitants in 2017 (p < 0.05) (Figure 1).
The overall hospitalization rates during the study period were 4.1 (95% CI: 4.0–4.2) per 100,000 inhabitants when RA was coded as the main diagnosis and 39.7 (95% CI: 39.6–39.8) when it was a comorbidity at admission. The highest annual hospitalization rate for RA as the main diagnosis was 8.1 (95% CI: 7.9–8.2) per 100,000 inhabitants in 2003, whereas the lowest was 1.9 (95% CI: 1.8–2.0) in 2017; overall, there was a declining trend since 2003. Conversely, the data displayed an increasing trend of annual hospitalization rates when RA was a comorbidity; the lowest rate was in 2002: 24.5 (95% CI: 24.1–24.9) per 100,000 inhabitants, whereas the highest was in 2017: 54.5 (95% CI: 54.0–54.9) per 100,000 inhabitants (Table 2).
Rheumatoid arthritis as the main diagnosis or comorbidity on admission.When RA was the main diagnosis, a total of 29,809 hospitalizations were recorded during the study period, with a hospitalization rate of 4.1 (95% CI: 3.9–4.3) per 100,000 population-years. The mean age of the patients admitted was 60.4 ± 14.7 years, and 71.6% of the patients were women. The average hospital stay was 7.1 ± 8.3 days, and the average cost per hospitalization was 3,503 ± 2,224 euros. RA (code 714.0) was classified as the main diagnosis in 9.2% of cases, followed by rheumatic lung and non-specific inflammatory polyarthropathy in 0.1% and 0.03% of cases, respectively. The rest of the variants of RA were classified as the main diagnosis in less than 0.03% of cases (Table 3). Amongst the 285,381 hospitalizations of patients with RA as a comorbidity, the most frequent causes of admission were diseases of the circulatory system (n = 54,123, 18.9%), diseases of the respiratory system (n = 49.876, 17.4%) and diseases of the osteomyoarticular system and connective tissue (n = 32.003, 11.2%) (Table 4).
Regional rates of hospitalization for rheumatoid arthritis in Spain. In Spain, the highest rates of hospitalization for RA per 100,000 population-years by autonomous communities (as the main diagnosis or comorbidity) were found in Castilla y León (69.9), Cantabria (69.9), Asturias (62.1) and Extremadura (55.8). By contrast, the lowest rates were found in Melilla (16.7), Ceuta (17.1), Canary Islands (27.9) and Balearic Islands (30.1) (Figure 2).