title: Trend for decreasing Multiple Sclerosis Severity Scores (MSSS) with increasing calendar year of enrollment into the New York State Multiple Sclerosis Consortium.
abstract: BACKGROUND
  Although the natural history of multiple sclerosis has been charted extensively, it is still not known whether the trajectory of disability accumulation has changed in the era of disease-modifying therapies (DMTs).
  
  
  OBJECTIVE
  The objective of this study was to examine trends in Multiple Sclerosis Severity Score (MSSS) with regard to calendar year of enrollment into the New York State MS Consortium (NYSMSC).
  
  
  METHODS
  Distributions of MSSS were calculated for each year of enrollment, from 1996 to 2007. Quantile regression was used in a multivariable analysis to model for conditional distribution of MSSS quantiles as functions of potential confounders.
  
  
  RESULTS
  The cohort consisted of 6238 patients. Mean age at enrollment was 38 years (SD=10) and mean disease duration was 10.1 years (SD=7.3); 57% were on DMTs. The quantile regression model of trends in MSSS between 1996 and 2007 controlled for age, sex, ethnicity, diagnostic delay, and disease duration and demonstrated a robust trend toward lower MSSS with increasing year of enrollment. The model-predicted median MSSS at enrollment in 1996 was 5.04 (95% CI, 4.86-5.21), and in 2007 was 3.78 (95%CI, 3.36-4.20; p<0.001). The downward trend in MSSS during the enrollment period was confirmed by analysis of Expanded Disability Status Scale (EDSS) distributions, adjusted for disease duration, in successive years of enrollment.
  
  
  CONCLUSIONS
  The recent enrollees into the NYSMSC had lower MSSSs compared to the earlier enrollees. The apparent slowing in disability accumulation is likely due to a complex combination of factors: advent of DMTs and improvements in MS care, as well as selection, migration, and recall biases.
authors.affiliation: Multiple Sclerosis Care Center, Department of Neurology, New York University School of Medicine, NYU-Hospital for Joint Diseases, 301 East 17th Street, New York, NY 10003–3804, USA. ilya.kister@gmail.com
authors.forename: Ilya
authors.initials: I
authors.lastname: Kister
authors.forename: Eric
authors.initials: E
authors.lastname: Chamot
authors.forename: Joshua H
authors.initials: JH
authors.lastname: Bacon
authors.forename: Gary
authors.initials: G
authors.lastname: Cutter
authors.forename: Joseph
authors.initials: J
authors.lastname: Herbert
mesh_terms: D000328:Adult; D015982:Bias; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D007155:Immunologic Factors / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D020528:Multiple Sclerosis, Chronic Progressive / Q000175:diagnosis* / Q000188:drug therapy / Q000453:epidemiology; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000175:diagnosis* / Q000188:drug therapy / Q000453:epidemiology; D009518:New York / Q000453:epidemiology; D011237:Predictive Value of Tests; D012042:Registries; D012044:Regression Analysis; D012720:Severity of Illness Index; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D007155:Immunologic Factors