The Phenotypes of Multiple Sclerosis Differ Significantly in Relative and Excess Mortality.

BACKGROUND

Patients With Multiple Sclerosis (MS) Have Higher Mortality Than Matched Background Populations. We Compare Relative and Excess Mortality in MS Over the Matched Background Populations Between Primary Progressive MS (PPMS), relapsing Onset MS (ROMS), and Secondary Progressive MS (SPMS).

METHODS

We included all patients from the nationwide and complete Danish MS Registry with onset 1994-2022 and compared the extra mortality of the MS phenotypes in terms of relative and excess mortality, with adjustment for sex, age at onset, disease-modifying treatment, and number of recorded relapses. We calculated the adjusted ratios of relative and excess mortalities between PPMS and ROMS and between PPMS and SPMS.

RESULTS

The initial course was unknown in 221, leaving 1412 cases with PPMS (which includes progressive relapsing MS) and 12,449 cases with ROMS. 627 had died during follow-up by the end of 2022. After adjustment, both ratios between PPMS and ROMS came close to unity, indicating that the excess mortality is equal for PPMS and ROMS in the long run. The adjusted relative and additive mortalities were factors 6.05 (95% CI 4.42-8.27) and 1.90 (95% CI 1.65-2.18) higher in SPMS than in PPMS.

CONCLUSIONS

Compared with the matched population, the adjusted relative and excess mortalities are the same for PPMS and ROMS. However, SPMS had a higher relative and excess mortality than PPMS, probably in part owing to the burden of disease carried over from the pre-progressive phase. This underlines the need for effective treatment in this later stage of the disease and more attention to comorbidity.