Disease-modifying drugs, multiple sclerosis and infection-related healthcare use in British Columbia, Canada: a population-based study

Abstract

Much remains unknown surrounding the disease-modifying drugs (DMDs) used to treat multiple sclerosis and infection-related healthcare use in the 'real-world' setting. We examined if DMD exposure was associated with altered infection-related healthcare use. We assessed if DMD (versus no) exposure was associated with altered infection-related hospitalizations, physician claims, and prescriptions filled in British Columbia, Canada (1996-2017). Healthcare use was assessed using negative binomial and proportional means regression models, reported as sex-/age-/comorbidity-/calendar year-/socioeconomic-adjusted rate and hazard ratios [aRR, aHR], with 95% confidence intervals [CIs]). We identified 19,360 multiple sclerosis cases (13,940/19,360; 72.0% women; mean age at study start=44.5 standard deviation, SD=13.3; mean follow-up=11.7 [SD=7.3] years). Relative to unexposed periods, exposure to any DMD was associated with a lower infection-related rate of physician claims (aRR=0.88; 95% CI:0.85-0.92) and hazard of hospitalization (aHR=0.64; 95% CI:0.56-0.73), and a higher rate of infection-related prescriptions (aRR=1.14; 95% CI:1.08-1.20). Exposure to any injectable or oral DMD was associated with a lower infection-related rate of physician claims (injectable aRR=0.88; 95% CI:0.84-0.92, oral aRR=0.83; 95% CI:0.77-0.90) and hazard of hospitalization (injectable aHR=0.65; 95% CI:0.56-0.75, oral aHR=0.54; 95% CI:0.38-0.77), whereas intravenous DMD exposure was not (aRR=0.99; 95% CI:0.86-1.14, aHR=0.73; 95% CI:0.49-1.09). Exposure to any injectable or intravenous DMD was associated with a higher rate of infection-related prescriptions (injectable aRR=1.15; 95% CI:1.08-1.22, intravenous=1.34; 95% CI:1.15-1.56), whereas oral DMDs were not (aRR=0.98; 95% CI:0.91-1.05). DMD exposure for the treatment of MS was associated with differences in infection-related healthcare use. While infection-related hospitalizations and physician visits were lower, prescription fills were higher. How these differences in infection-related healthcare use affect outcomes in persons with multiple sclerosis warrants consideration. Canadian Institutes of Health Research (CIHR); German Research Foundation (DFG).