Hospitalizations due to systemic connective tissue diseases: Secular trends and regional disparities in Sweden, 1998-2016.

AIM: To investigate secular trends and regional disparities in hospitalizations due to systemic connective tissue diseases (SCTD) in Sweden from 1998 to 2016.

METHOD: We identified all hospital admissions with a principal diagnosis of SCTD (ICD-10 codes: M30-M36) from the Swedish National Patient Register. Joinpoint regression was used to assess secular trends in age-standardized hospitalization rates (ASHR) and proportions of SCTD from all and musculoskeletal disorders hospitalizations. We also assessed the secular trends in the absolute and relative regional disparities of SCTD hospitalizations.

RESULTS: We identified 89 333 SCTD hospitalizations (0.3% of all hospitalizations), of these about 69% were for women and 49% of patients were aged 15-64 years. Polyarteritis nodosa and related conditions (PANRC) and systemic lupus erythematosus (SLE) were the most frequent SCTD among those aged <10 years and 10-54 years, respectively. Joinpoint regression suggested that both rates and proportions of SCTD hospitalizations declined over time. These trends persisted among sex, age and diagnosis subgroups except for PANRC in patients aged 0-19 years who observed an average annual increase of 3.4% (95% CI: 1.8, 5.1) over the study period. There were 2.4-fold (95% CI: 2.3-2.5) difference between the regions with the highest and lowest mean ASHR. There was no statistically significant secular trend in the relative regional disparities, whereas the absolute regional disparity declined over time.

CONCLUSION: There were substantial decreases in the absolute and relative burden of SCTD hospitalizations reflecting possible improvements in disease management in Sweden. The rising trend in PANRC among the youngest children warrants further investigation.