Mortality of multiple sclerosis in Iceland population-based mortality of MS in incidence and prevalence cohorts

INTRODUCTION: Mortality is an important feature of the natural history of multiple sclerosis (MS). We report the mortality of all individuals with MS in Iceland, identified in a nationwide population-based study. PATIENTS AND METHODS: The results are based on a prevalence cohort and an incidence cohort. The prevalence cohort consisted of all patients with MS (n = 526) living in Iceland on the 31 December 2007. The incidence cohort consisted of all residents of Iceland (n = 222) diagnosed with MS during 2002 to 2007. Mortality was determined by following both the incidence cohort (from diagnosis) and the prevalence cohort (from the prevalence day) until death or 31 December 2020. The mortality, associated with MS, was compared with that expected in the Icelandic population (standardized mortality ratio (SMR)). RESULTS: (a) Prevalence cohort (n = 526). The mean follow up was 12.0 years (range 0.3–13.0). The SMR was 1.6 (95% confidence interval (CI) 1.3–2.0). (b) Incidence cohort (n = 222). The mean follow up was 15.4 years (range 3.7–18.5). The SMR was 1.2 (95% CI 0.6–2.2). CONCLUSION: During the follow-up period, there was a substantial increase in mortality among the patients with MS, compared with the general population. There was no increase in mortality among the incidence cohort, when followed for up to 18.5 years following diagnosis.