The effect of national disease-modifying therapy subsidy policy on long-term disability outcomes in people with multiple sclerosis.

Background: Disease-modifying therapies (DMTs) are used to treat people with relapsing-onset multiple sclerosis (ROMS), but our knowledge is largely limited to their short-term effects.

Objective: To determine (1) the impact of national-level DMT subsidy policy on DMT use and health outcomes in people with MS (PwMS) and (2) the long-term effects of DMT on disability and quality of life (QoL; 5-level EQ-5D version (EQ-5D-5L) utility value).

Methods: This observational cohort study compared Australian and New Zealand populations with different levels of DMT availability 10-20 years post-ROMS diagnosis. Between-country differences were assessed using standardised differences. Associations were assessed with multivariable linear regression models.

Results: We recruited 328 Australians and 256 New Zealanders. The Australian cohort had longer DMT treatment duration, greater proportion of disease course treated and shorter duration between diagnosis and starting DMT. The Australian cohort had lower median Expanded Disability Status Scale (EDSS) (3.5 vs 4.0) and Multiple Sclerosis Severity Score (MSSS) (3.05 vs 3.71) and higher QoL (0.71 vs 0.65). In multivariable models, between-country differences in disability and QoL were largely attributed to differential use of DMT.

Conclusions: This study provides evidence for the impact of national-level DMT policy on disability outcomes in PwMS. Where DMTs are more accessible, PwMS experienced less disability progression and improved QoL 10-20 years post-diagnosis.