Incidence of Multiple Sclerosis in Germany: A Cohort Study Applying Different Case Definitions Based on Claims Data.

BACKGROUND: Data on the incidence of multiple sclerosis (MS) on the national level is scarce. We aimed to estimate the incidence of MS in Germany and to compare different MS case definitions based on claims data.

METHODS: We conducted a cohort study with the German Pharmacoepidemiological Research Database in 2012 and calculated age- and gender-standardized incidence rates (sIRs) for 3 case definitions. In addition, the effect of stepwise reduction of the look-back period without MS diagnosis on the incidence rate was evaluated.

RESULTS: Our cohort comprised 4,175,877 individuals. The first case definition based on ICD-10 diagnoses yielded an sIR of 21.8 (95% CI 20.2-23.5) per 100,000 person years, whereas the second and third case definitions with additional requirements for drug treatment and diagnostic tests resulted in lower sIRs of 10.1 (9.1-11.3) and 6.6 (5.8-7.6) respectively. We observed a higher incidence for shorter look-back periods.

CONCLUSION: The incidence of MS in Germany might be substantially higher than suggested in earlier studies. In addition, our study highlights the importance of a look-back period of at least 36 months to identify incident MS cases based on claims data.