BACKGROUND: In multiple sclerosis (MS), confirmed disability progression (CDP) can be either the result of progression independent of relapse activity (PIRA) or relapse-associated worsening (RAW). However, the economic effect of PIRA and RAW on societal economic costs in patients with MS is not well understood.

OBJECTIVE: To determine societal economic costs of patients achieving disease activity free status (DAF) and compare them with those having PIRA and RAW events.

METHODS: We used a roving EDSS score analysis to detect PIRA and RAW events with confirmation after at least 6 months. We estimated the age-, gender-, EDSS-adjusted effects of PIRA and RAW on total, direct medical, direct non-medical and indirect societal economic costs. Patients achieving DAF were assigned to as reference.

RESULTS: Overall, 1959 patients were analyzed. Total mean quarterly societal economic costs including disease-modifying therapies (DMTs) were 6929€ (SD: 2886€) per patient averaged over a period of 2 years. Excluding DMTs, patients achieving DAF had total mean quarterly costs of 1703€ (SD: 2489€). PIRA caused 29% (IRR: 1.29; CI 1.06-1.50, p < 0.05) higher total costs compared to DAF. On the contrary, RAW increased total costs by factor 1.56 (CI 1.30-1.87, p < 0.001). The effect of PIRA and RAW was striking for direct medical costs which increased by factor 1.48 (95% CI 1.13-1.95, p < 0.01) and 2.25 (95% CI 1.72-2.94, p < 0.001), respectively.

CONCLUSION: Disease progression increases societal economic costs significantly. Thus, delaying or even preventing disease progression in MS may reduce the societal economic burden of MS.