Comprehensive analysis of multiple sclerosis hospitalization trends in Spain (1998-2022)

Objective: To analyse the trends in MS hospitalization rates in Spain (1998-2022) considering age, period, and birth cohort (A-P-C) effects. Methods: This retrospective study used data on MS hospitalizations from the Spanish National Health System Minimum Basic Data Set (CMBD). Age-Standardized Hospitalization Rates (ASHRs) and Joinpoint analysis were used to assess trends. A-P-C analysis was performed to estimate age-specific rates, period and cohort effects. Results: From 1998 to 2022, MS hospital admissions in Spain declined annually by -2.1 %, with women showing a slightly greater decrease (-2.3 %) than men (-1.7 %). Joinpoint analysis revealed non-parallel trends, with three inflection points indicating distinct periods of stabilization and decline. ASHR showed an overall decrease, with -2.0 % for men and -2.2 % for women annually. Risk of hospitalization peaked in the 25-29-year age group for men and 30-34-year age group for women, declining with age. Women consistently had higher risk ratios across age groups. Cohort analysis showed periods of stabilization and decline in MS hospitalization risk, aligning with joinpoint analysis findings. Risk increased for cohorts born in the early 20th century, peaking around 1938, followed by a progressive decline in later cohorts. Conclusions: Despite an aging population, MS hospitalization rates in Spain decreased. The risk of hospitalization for MS is affected by a person's age, the time period they were born in, the historical context of healthcare received, and potentially their sex.