PARIS—Interferon beta is associated with a lower risk of all-cause mortality among patients with multiple sclerosis (MS) treated in clinical practice, according to data presented at the Seventh Joint ECTRIMS–ACTRIMS Meeting. Participants in the study were observed for as long as 18 years. The findings were consistent across two geographically distinct regions (ie, Canada and France), said the investigators.
Interferon beta has benefits for patients with MS, but whether the treatment prolongs survival in this population is unclear. Elaine Kingwell, PhD, a research associate in the Division of Neurology at the University of British Columbia in Vancouver, and colleagues investigated the association between interferon beta treatment and all-cause mortality in the clinical setting.
The researchers accessed prospectively collected data on patients with relapsing-remitting MS at onset, including sex, birth date, Expanded Disability Status Scale (EDSS) scores, and disease modifying treatments (DMTs), from British Columbia, Canada, and Rennes, France. Data were linked to population-based administrative databases capturing death dates in both countries. In Canada, data about drug prescriptions filled, universal health care registration, hospital admissions, and physician visits also were available. Patients were treatment-naïve at study entry, and investigators followed them from the earliest of first MS clinic visit, 18th birthday, or January 1, 1996, to the earliest of death, emigration, or December 31, 2013.
Using a nested case–control design, the researchers randomly selected as many as 20 MS controls by incidence density sampling and matched them to MS cases (ie, patients who died during follow-up) by sex, age (± 5 years), calendar year, and EDSS score at study entry. The association between all-cause mortality and interferon beta exposure (greater than six months) was estimated by conditional logistic regression, expressed as odds ratios (OR), and adjusted for glatiramer acetate (greater than six months exposure), any exposure to another DMT, age, and comorbidity burden. Analyses were stratified by sex and country. The researchers examined the association with cumulative exposure to interferon beta (up to three years or more than three years).
The cohort included 7,009 patients (75% women) with relapsing-remitting MS with a median age at study entry of 42. During follow-up (median, 12.3 years), 30% of participants were exposed to interferon beta, 11% were exposed to glatiramer acetate, and 12% were exposed to other DMTs, including MS-specific immunosuppressants. As many as 20 controls were successfully matched to each of 649 cases (mean age at death, 60). The odds of exposure to interferon beta was 32% lower among cases than controls. Stratification by sex or country did not change the interpretation of findings. Compared with no or minimal exposure, a longer cumulative time on interferon beta (ie, more than three years) was associated with increased survival (OR, 0.44), whereas exposure of less than three years was not (OR, 1.00).