Trajectories of disease-modifying therapies and associated sickness absence and disability pension among 1923 people with multiple sclerosis in Sweden

Background: There is limited information on the trajectories of disease-modifying therapy (DMT) use and their association with sickness absence and/or disability pension (SADP) among people with multiple sclerosis (PwMS). The objective of the study was to identify trajectories of DMT use over 10 years among PwMS, identify sociodemographic and clinical factors associated with the trajectories, and to assess the association between identified trajectories and SADP days.Methods: A longitudinal register-based study was conducted, on a prospective data set linked across six nationwide registers, assessing treatment courses of PwMS with DMTs for the 10 years following multiple sclerosis (MS) onset. The study included 1923 PwMS with MS onset in 2007-2010, when aged 19-56 years. In each 6-month-period, their treatment was categorized as before treatment, high-efficacy, non-high-efficacy, or no DMT. Sequence analysis was performed to identify sequences of the treatment categories and cluster them into different DMT trajectories. Cluster belonging, in relation to demographic and clinical characteristics, was assessed through log-multinomial regression analysis. The association of trajectories/cluster-belonging with SADP net days was assessed using generalized estimating equation (GEE) models.Results: Cluster analyses identified 4 trajectories of DMT use: long-term non-high-efficacy DMTs (38.6%), escalation to high-efficacy DMTs (31.2%), delayed start and escalation to high-efficacy DMTs (15.4%), and discontinued/ no DMT (14.2%). Age, MS type, expanded disability status scale (EDSS) score and the number of DMT switches were associated with cluster belonging. The youngest age group (18-25) were more likely to be in the escalation to high-efficacy cluster. People with primary progressive MS were more likely to be in the delayed start or discontinued/ no DMT cluster. Higher EDSS scores were associated to being in the other three clusters than in the long-term non-high-efficacy DMTs cluster. Higher number of DMT switches were associated with being in the escalation to high-efficacy DMTs cluster but less likely to be in the delayed start or discontinued/ no DMT clusters. Descriptive analyses showed a trend of fewer mean SADP days among PwMS using non-high-efficacy DMT than the other clusters about 9 years after onset. PwMS in the escalation to high-efficacy and discontinued/no DMT clusters had more SADP days. PwMS in the delayed start and escalation to high-efficacy DMTs cluster, started with fewer SADP days which increased over time. SADP days adjusted through GEE models showed trends comparable with the descriptive analysis.Conclusion: This study described the long-term real-world trajectories of DMT use among PwMS in Sweden using sequence analysis and showed the association of the trajectories with SADP days as well as sociodemographic and clinical characteristics.