|EDSS, Expanded Disability Status Scale. |
Baseline was considered as the first date a patient became eligible for interferon beta treatment (whilst being >=50 years old).
Untreated patients who first became eligible for treatment in the “interferon beta era” (whilst being >=50 years old).
Comparison of the interferon beta-treated patients with the contemporary untreated patients.
Untreated patients who first became eligible for treatment in the “pre-interferon beta era” (whilst being >=50 years old).
Comparison of the interferon beta-treated patients with the historical untreated patients.
Pearson’s chi-square test.
If this period included MS onset, the first onset attack was not included as a relapse.
Deyo adaptation of the Charlson comorbidity index, based on hospital admissions or physician visits in the two years prior to baseline and derived from International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) codes, excluding hemiplegia, paraplegia, and dementia to avoid misclassifying complications of MS as comorbidity. All relevant comorbidities were aggregated into a single variable theoretically ranging from 0 to 33; higher scores indicate more comorbidity.
Used as a proxy for socioeconomic status. Data were missing for 2 patients in the interferon beta-treated cohort and 8 patients in the contemporary control cohort.