Systematic literature review and meta-analysis of the prevalence of secondary progressive multiple sclerosis in the USA, Europe, Canada, Australia, and Brazil

Abstract

Background Secondary progressive multiple sclerosis (SPMS) is a subtype of multiple sclerosis (MS), which is a chronic neurological disease, characterised by inflammation of the central nervous system. Most of MS patients eventually progress to SPMS. This study estimates the prevalence of SPMS in the United States of America, Europe, Canada, Australia, and Brazil. Methods A systematic literature search of the Medline and Embase databases was performed using the OVID™ SP platform to identify MS epidemiological studies published in English from database inception to September 22, 2020. Studies reporting the prevalence of MS and proportion of SPMS patients in the included population were selected. The pooled prevalence of SPMS was calculated based on the proportion of SPMS patients. The Loney quality assessment checklist was used for quality grading. A meta-analysis of the proportions was conducted in RStudio. Results A total of 4754 articles were retrieved, and prevalence was calculated from 97 relevant studies. Overall, 86 medium- and high-quality studies were included in the meta-analysis. Most studies were conducted in European countries (84 studies). The estimated pooled prevalence of SPMS was 22.42 (99% confidence interval: 18.30, 26.95)/100,000. The prevalence of SPMS was more in the North European countries, highest in Sweden and lowest in Brazil. A decline in SPMS prevalence was observed since the availability of oral disease-modifying therapies. We also observed a regional variation of higher SPMS prevalence in urban areas compared with rural areas. Conclusion High variability was observed in the estimated SPMS prevalence, and the quality of the studies conducted. The influence of latitude and other factors known to affect overall MS prevalence did not fully explain the wide range of inter-country and intra-country variability identified in the results.

Proportion and characteristics of secondary progressive multiple sclerosis in five European registries using objective classifiers

“…This is in good accordance with the classic proportion of 27% SPMS in the Lyon natural history cohort 13 and other population-based estimations. 25 Importantly, we find that the algorithms propose reclassification more often among patients that are younger, female, have more relapses, and are on DMTs. Since young age, female sex, and relapses are characteristics of RRMS, it should be expected that such events tend to delay a correct assignment of conversion to SPMS, but can alternatively reflect less than optimal specificity of the objective classifiers.…”

“…This is in good accordance with the classic proportion of 27% SPMS in the Lyon natural history cohort 13 and other population-based estimations. 25…”

Secondary Progressive Multiple Sclerosis

“…The prevalence of SPMS varies globally (1-58 per 100,000 general population). 3,4 In the European Union (EU), SPMS prevalence ranges from 3-50 per 100,000 whereas in the United States (US), the prevalence is estimated at 27-45 per 100,000. 3 Although the onset of SPMS is identified as a "key turning point" in the MS disease continuum, SPMS is always diagnosed retrospectively by the subjective judgment of the clinician, e3-e5 i.e., after evidence of irreversible disability accrual on the Expanded Disability Status Scale (EDSS) becomes noticeably apparent, a process that can take up to 3 or more years.…”

“…3,4 In the European Union (EU), SPMS prevalence ranges from 3-50 per 100,000 whereas in the United States (US), the prevalence is estimated at 27-45 per 100,000. 3 Although the onset of SPMS is identified as a "key turning point" in the MS disease continuum, SPMS is always diagnosed retrospectively by the subjective judgment of the clinician, e3-e5 i.e., after evidence of irreversible disability accrual on the Expanded Disability Status Scale (EDSS) becomes noticeably apparent, a process that can take up to 3 or more years. The inherent uncertainty as to whether disability in patients with relapsing MS is permanent or will resolve leads to a period of diagnostic uncertainty termed as the "transition phase" that delays the SPMS diagnosis.…”

“…The prevalence of SPMS varies globally (1–58 per 100,000 general population). 3,4 In the European Union (EU), SPMS prevalence ranges from 3–50 per 100,000 whereas in the United States (US), the prevalence is estimated at 27–45 per 100,000. 3…”