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. 2025 Mar 16;11(1):20552173251326173.
doi: 10.1177/20552173251326173. eCollection 2025 Jan-Mar.

Incidence and prevalence of multiple sclerosis during eras of evolving diagnostic criteria-a nationwide population-based registry study over five decades

Anna Maunula  1   2 , Sini M Laakso  1   3 , Matias Viitala  4 , Merja Soilu-Hänninen  5   6 , Marja-Liisa Sumelahti  7 , Sari Atula  3   8
Affiliations

Incidence and prevalence of multiple sclerosis during eras of evolving diagnostic criteria-a nationwide population-based registry study over five decades

Anna Maunula et al. Mult Scler J Exp Transl Clin. .

Abstract

Background: Impact of changing diagnostic criteria for the population-based incidence of multiple sclerosis (MS) has not been investigated.

Objective: To assess the effect of changing diagnostic criteria on national MS incidence and prevalence in Finland from 1974 to 2021.

Methods: We identified patients with MS (pwMS) through the National MS registry and the national Care Register for Healthcare and divided them into four groups based on the year of MS diagnosis: 1) Schumacher criteria (1974-1982), 2) Poser criteria (1983-2000), 3) Earlier McDonald criteria (2001-2016), and 4) Current McDonald criteria (2017-2021). Age-adjusted incidence and prevalence were calculated.

Results: Age-adjusted incidence per 105 person years increased from 3.7 (95% CI 3.5-3.8) during the Schumacher criteria period to 9.2 (95% CI 9.0-9.4) during the earlier McDonald criteria. During the Current McDonald criteria incidence stabilized to 8.6 (95% CI 8.3-9.0). Prevalence increased from 24.3 (95% CI 22.8-25.8) to 241.5 (95% CI 237.3-245.6) per 105 person years.

Conclusion: Both incidence and prevalence of MS increased significantly. Incidence showed a sharp increase when entering the twenty-first century, after which it stabilized. Increasing incidence was likely related to incorporation of MRI in the diagnostic criteria. Current diagnostic criteria did not further increase the incidence.

Keywords: MS; Multiple sclerosis; diagnostic criteria; epidemiology; incidence; prevalence.

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Figures

Figure 1.
Figure 1.
Flow chart of the process of forming the cohort.
Figure 2.
Figure 2.
Incidence of MS during the diagnostic eras. Values are point estimates for each diagnostic era separately. (a) Age-adjusted incidence per 105 person years by eras of diagnostic criteria. (b) Age-specific incidence per 105 person years by age group at diagnosis shown for different eras of diagnostic criteria.
Figure 3.
Figure 3.
Trend of age-adjusted prevalence per 105 person years from 1974 to 2021. C.McD. Criteria = Current McDonald Criteria.
See this image and copyright information in PMC

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