The impact of the COVID-19 pandemic on the incidence and clinical disease activity of multiple sclerosis

Purpose: The aim of this study was to describe temporal trends in multiple sclerosis (MS) incidence and relapse frequency in Türkiye across pre-pandemic, pandemic, and post-pandemic periods, and to assess whether the pandemic was associated with population-level changes. Materials and Methods: This retrospective, nationwide population-based study used the Turkish national healthcare database. Newly diagnosed MS cases recorded between January 2018 and December 2023 were analyzed to assess incidence trends. Relapses were identified using prescription and procedure records, including high-dose intravenous methylprednisolone (≥3 consecutive days, ≥1500 mg cumulative dose, ≥30-day interval) and plasmapheresis as a marker of severe relapse. Annualized relapse rates (ARRs) with 95% confidence intervals were calculated for 2018–2023. Results: MS incidence declined sharply in early 2020, coinciding with nationwide lockdowns, but returned to pre-pandemic levels thereafter. Relapse activity showed a transient decrease in 2020, followed by a temporary increase in 2021 (ARR 0.057), and stabilization in 2022–2023. Overlapping confidence intervals across years indicated no sustained change. Conclusion: The COVID-19 pandemic was not associated with a lasting change in MS incidence in Türkiye but was accompanied by temporary fluctuations in relapse frequency. These findings highlight the resilience of MS epidemiology and emphasize the importance of maintaining continuity of care during public health crises.