Prevalence and incidence of ischemic heart disease in multiple sclerosis: A population-based validation study

Background: Studies suggest an altered risk of ischemic heart disease (IHD) in multiple sclerosis (MS), but data are limited. We aimed to validate and apply administrative case definitions to estimate the incidence and prevalence of IHD in MS. Methods: Using administrative data we identified persons with incident MS (MSPOP) and a matched general population (GPOP) cohort. We developed case definitions for IHD using ICD-9/10 codes and prescription claims, compared them to medical records, then applied them to evaluate the incidence and prevalence of IHD. Results: Agreement between medical records and the administrative definition using >= 1 hospital or >= 2 physician claims over 5 years was moderate (kappa=0.66; 95% CI: 0.42-0.90). In 2005, the age-standardized prevalence of IHD was 6.77% (95% CI: 5.48-8.07%) in the MSPOP and 6.11% (95% CI: 5.56-6.66%) in the GPOP. The prevalence of IHD was higher in the MSPOP than the GPOP among persons aged 20-44 years (prevalence ratio 1.87; 95% CI: 1.65-2.12) and aged 45-59 years (prevalence ratio 1.21; 95% CI: 1.08-1.35). The incidence of IHD was also higher in the MSPOP (incidence rate ratio 1.24; 95% CI: 0.97-1.59). Conclusions: More than 5% of the MSPOP has IHD. The incidence of IHD was higher than expected in persons aged <60 years. Further evaluation of this issue is warranted. (C) 2013 Elsevier B.V.