Background: As healthcare management of highly active-relapsing-remitting multiple sclerosis (HA-RRMS) patients is more complex than for the whole multiple sclerosis (MS) population, this study assessed the related economic burden from a National Health Insurance's (NHI's) perspective.

Methods: Study based on French NHI databases, using individual data on billing and reimbursement of outpatient and hospital healthcare consumption, paid sick leave and disability pension, over 2010-2017.

Results: Of the 9,596 HA-RRMS adult patients, data from 7,960 patients were analyzed with at least 2 years of follow-up. Mean annual cost/patient was €29,813. Drugs represented 40% of the cost, hospital care 33%, disability pensions 9%, and all healthcare professionals' visits combined 8%. Among 3,024 patients under 60 years-old with disability pension, disability pension cost €7,168/patient/year. Among 3,807 patients with paid sick leave, sick leave cost €1,956/patient/year. Mean costs were €2,246/patient higher the first year and increased by €1,444 between 2010 and 2015, with a €5,188 increase in drug-related expenditures and a €634 increase in healthcare professionals' visits expenditures but a €4,529 decrease in hospital care expenditures.

Conclusions: The cost of health care sick leaves, and disability pensions of HA-RRMS patients was about twice as high as previously reported cost of MS patients.