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Has the risk of reaching disability milestones in multiple sclerosis changed over the last decade?
In this nationwide population-based cohort study of 7331 patients with multiple sclerosis diagnosed between 1995 and 2010, a significant 3% decrease per calendar year of diagnosis for the risk of sustained Expanded Disability Status Scale score (EDSS) 3.0, a significant 6% decrease for the risk of EDSS 4.0, and a significant 7% decrease for the risk of EDSS 6.0 among patients with relapsing-onset multiple sclerosis was found.
The risk of reaching disability milestones decreased significantly over the last decade in patients with relapsing-onset multiple sclerosis in Sweden.
Clinicians’ experience and findings from recent natural history studies suggest that multiple sclerosis (MS) may now be running a more slowly progressing course than before.
To investigate whether the risk of reaching MS disability milestones has changed over the last decade in Sweden.
Design, Setting, and Participants
A nationwide population-based retrospective cohort study. By April 2017, 12 512 patients with available information on demographics, MS phenotype, and date of MS onset and diagnosis were registered in the Swedish MS Registry of which 7331 patients with at least 2 recorded Expanded Disability Status Scale scores (EDSS) and diagnosed between January 1995 and December 2010 were included. No further exclusion criteria were applied. Patients were followed up until December 2016 with a median duration follow-up of 8.5 (interquartile range, 4.7-13.8) years. Statistical analysis began in April 2017.
Main Outcomes and Measures
Patients were followed up from MS onset date to the date of sustained EDSS 3.0, 4.0, and 6.0. To handle interval-censored observations, a Weibull model was fit, and the change in the risk of EDSS 3.0, 4.0, and 6.0 over calendar years was estimated and hazard ratios (HRs) with corresponding CIs were calculated.
Of 7331 patients, 5196 (70.9%) were women, and the mean (SD) age at diagnosis was 38.3 (11.7) years. Adjusting for sex, number of clinic visits, diagnostic delay, and onset age, a 3% decrease per calendar year of diagnosis for the risk of sustained EDSS 3.0 (HR, 0.97; 95% CI, 0.96-0.97), a 6% decrease for the risk of EDSS 4.0 (HR, 0.94; 95% CI, 0.93-0.95), and a 7% decrease for the risk of EDSS 6.0 (HR, 0.93; 95% CI, 0.91-0.94) among patients with relapsing-onset MS was found. The trends were not significant for patients with progressive-onset MS (EDSS 3.0: HR, 1.01; 95% CI, 0.98-1.03; EDSS 4.0: HR, 1.00; 95% CI, 0.98-1.02; EDSS 6.0: HR, 1.00; 95% CI, 0.98-1.02).
Conclusions and Relevance
Risk of reaching major disability milestones has significantly decreased over the last decade in patients with relapsing-onset MS in Sweden. Several factors could potentially be responsible for this observation. However, given that no change was seen in disability accrual of patients with progressive-onset MS and the absence of efficacious treatment option in this group, increased use of more efficacious disease-modifying treatments could be a possible driver of this change.
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Corresponding author: Jan Hillert, MD, PhD, Department of Clinical Neuroscience, Karolinska Institutet, Widerströmska huset, Tomtebodavägen 18, 171 77 Solna, Stockholm, Sweden (firstname.lastname@example.org).
Accepted for Publication: December 18, 2018.
Published Online: March 18, 2019. doi:10.1001/jamaneurol.2019.0330
Author Contributions: Drs Beiki and Manouchehrinia had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Drs Manouchehrinia and Hillert contributed equally as co–last author.
Concept and design: Beiki, Manouchehrinia, Hillert.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Beiki, Manouchehrinia.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: All authors.
Obtained funding: Hillert.
Conflict of Interest Disclosures: Dr Beiki has received salary for epidemiological consultation for pharmaceutical companies from Cognizant Technology Solutions. Dr Hillert has received honoraria for serving on advisory boards for Biogen, Sanofi Genzyme, and Novartis, speaker’s fees from Biogen, Novartis, Merck Serono, Bayer Schering, Teva Pharmaceutical Industries, and Sanofi Genzyme; and has served as principal investigator for projects or has received unrestricted research support from Biogen Idec, Merck Serono, Teva Pharmaceutical Industries, Sanofi Genzyme, and Bayer Schering. No other disclosures were reported.
Funding/Support: This research was funded by the Swedish Research Council and the Swedish Brain Foundation.
Role of the Funder/Sponsor: The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
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