Hospital volume impact on multiple sclerosis outcomes: a retrospective cohort study using a nationwide administrative...

Hospital volume (HV) effect on multiple sclerosis (MS) outcomes remains largely unexplored, particularly in Japan, where access to advanced medical resources is abundant. This study evaluates the association between treatment at high-volume hospitals and improved MS outcomes, focusing on time to readmission due to relapse and length of stay (LOS) during relapse admissions.

We performed a retrospective cohort study using the Diagnosis Procedure Combination database and included 6647 patients admitted for MS relapse. HV was defined as the mean annual number of patients hospitalized with the MS diagnostic code and categorized into high and low groups with a median of 14.4. Time to readmission due to MS relapse was the primary outcome, while LOS was the secondary outcome. Inverse probability of treatment weighting was applied for covariate adjustment, and Cox proportional hazards model for evaluating primary outcomes.

The high-volume group had a significantly longer time to readmission due to MS relapse than did the low-volume group (hazard ratio, 0.87; 95 % confidence interval [CI]: 0.79-0.96, p = 0.005). This finding was consistent across different subgroups and remained robust in sensitivity analyses. In contrast, the LOS difference between the high and low-volume groups was insignificant (difference: -1.11 days, 95 % CI: -2.95 to 0.72, p = 0.234).

Our findings indicate that high-volume hospitals may provide more optimized relapse prevention therapies. Despite the modest effect size and inherent study limitations, further research is needed to explore the potential benefits of centralized MS care in Japan and other countries.