@article {zhang_beta-interferon_2015,
	title = {Beta-interferon exposure and onset of secondary progressive multiple sclerosis},
	journal = {European Journal of Neurology},
	volume = {22},
	number = {6},
	year = {2015},
	pages = {990{\textendash}1000},
	abstract = {<p>Background and purpose Beta-interferons (IFNβ) are the most widely prescribed drugs for patients with multiple sclerosis (MS). However, whether or not treatment with IFNβ can delay secondary progressive MS (SPMS) onset remains unknown. Our aim was to examine the association between IFNβ exposure and SPMS onset in patients with relapsing-remitting MS (RRMS). Methods A retrospective cohort study using British Columbia (Canada) population-based clinical and health administrative data (1985{\textendash}2008) was conducted. RRMS patients treated with IFNβ (n\&nbsp;=\&nbsp;794) were compared with untreated contemporary (n\&nbsp;=\&nbsp;933) and historical (n\&nbsp;=\&nbsp;837) controls. Cohort entry was the first clinic visit during which patients became eligible for IFNβ treatment (baseline). The outcome was time from baseline to SPMS onset. Cox regression models with IFNβ as a time-dependent exposure were adjusted for sex, and baseline age, disease duration, disability, *socioeconomic status and *comorbidities (*available for the contemporary cohorts only). Additional analyses included propensity score adjustment. Results The median follow-up for the IFNβ-treated, untreated contemporary and historical controls were 5.7, 3.7 and 7.3\&nbsp;years, and the proportions of patients reaching SPMS were 9.2\%, 11.8\% and 32.9\%, respectively. After adjustment for confounders, IFNβ exposure was not associated with the risk of reaching SPMS when either the contemporary or the historical untreated cohorts were considered (hazard ratio 1.07; 95\% confidence interval 0.93{\textendash}1.48, and hazard ratio 1.04; 95\% confidence interval 0.74{\textendash}1.46, respectively). Further adjustments and the propensity score yielded results consistent with the main analysis. Conclusions Amongst patients with RRMS, use of IFNβ was not associated with a delayed onset of SPMS.</p>
},
	keywords = {beta-interferon, cohort study, multiple sclerosis, progression},
	doi = {10.1111/ene.12698},
	url = {http://onlinelibrary.wiley.com/doi/10.1111/ene.12698/abstract},
	author = {Zhang, T and Shirani, A and Zhao, Y and Karim, ME and Gustafson, P and Petkau, J and Evans, C and Kingwell, E and van der Kop, M and Zhu, F and Oger, J and Tremlett, H and BC MS Clinic Neurologists}
}
@article { ISI:000345076200013,
	title = {Association between beta-interferon exposure and hospital events in multiple sclerosis},
	journal = {Pharmacoepidemiology and Drug Safety},
	volume = {23},
	number = {11},
	year = {2014},
	pages = {1213-1222},
	publisher = {WILEY-BLACKWELL},
	address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA},
	abstract = {<p>Purpose A systematic evaluation of hospital events can be an important surrogate measure for drug effectiveness or adverse effects. The purpose of this study was to examine the association between beta-interferon use and hospital events in a large cohort of patients with multiple sclerosis (MS). MethodsRetrospective cohort study comparing beta-interferon exposed and unexposed patients using clinical data from the British Columbia MS (BCMS) database linked with health administrative databases, 1996-2008. For each patient, the primary outcome was the number of hospital events in each month, analyzed by quasi Poisson regression. Beta-interferon exposure was examined two ways: current and cumulative exposure. Secondary outcomes included whether a hospital event occurred in each month for each specific primary diagnoses, grouped by International Classification of Diseases categories. ResultsCurrent exposure to beta-interferon was not associated with an altered rate of hospital events (adjusted incident rate ratio 1.018; 95\% CI 0.803-1.290). Similarly, there was no association with cumulative exposure. Cumulative beta-interferon exposure was associated with a lower odds of respiratory disease-related hospital events compared to those never exposed to beta-interferon. ConclusionsExposure to beta-interferon for MS was not associated with a change in overall hospital event rates. Preliminary evidence suggests that the beta-interferons may have a protective effect against respiratory diseases requiring hospitalization in MS patients. Copyright (c) 2014 John Wiley \&amp; Sons, Ltd.</p>
},
	keywords = {beta-interferon, hospitalization, multiple sclerosis, pharmacoepidemiology},
	doi = {10.1002/pds.3667},
	author = {Evans, C and Zhu, F and Kingwell, E and Shirani, A and van der Kop, ML and Petkau, J and Gustafson, P and Zhao, Y and Traboulsee, A and Oger, Joel and Tremlett, Helen}
}
