Association between disease-modifying therapies for multiple sclerosis and healthcare utilisation on a population level: a retrospective cohort study

Objective Disease-modifying therapy (DMT) use in multiple sclerosis (MS) has increased significantly. However, the impact of DMTs on healthcare use is limited and conflicting, and rarely examined at a population level. This study examined the association between DMTs and healthcare utilisation at the population level. Design Retrospective cohort. Setting Health administrative data from Saskatchewan, Canada (1997-2016). Participants To test for associations at the population level, we identified two cohorts. The general population cohort included all Saskatchewan residents >= 18 years who were drug plan beneficiaries. The MS cohort included individuals ? >= 18 years, identified using a validated definition (>= 3 hospital, physician or drug claims for MS). Main outcome measures and methods To test for an association between the total number of DMT dispensations per year and the total number of hospitalisations we used negative binomial regression fitted with generalised estimating equations (GEE); only hospitalisations that occurred after the date of MS diagnosis (date of first claim for MS or demyelinating disease) were extracted. To test for an association between the number of DMT dispensations and physician claims, negative binomial distributions with GEE were fit as above. Results were reported as rate ratios (RR), with 95% Cls, and calculated for every 1000 DMT dispensations. Results The number of DMT dispensations was associated with a decreased risk for all-cause (RR=0.994; 95% CI 0.992 to 0.996) and MS-specific (RR=0.909; 95% CI 0.880 to 0.938) hospitalisations. The number of DMT dispensations was not associated with the number of all-cause (RR=1.006; 95% CI 0.990 to 1.022) or MS-specific (RR=0.962; 95% CI 0.910 to 1.016) physician claims. Conclusion Increased DMT use in Saskatchewan was associated with a reduction in hospitalisations, but did not impact the number of physician services used. Additional research on cost-benefit and differing treatment strategies would provide further insight into the true impact of DMTs on healthcare utilisation at a population level.