Prevalence of treated epilepsy in western medicine among the adult population in Taiwan: a study conducted using antiepileptic drug prescription data.

Objective: To determine the prevalence of treated epilepsy in the Taiwan in 2004 using prescription data from the National Health Insurance (NHI) research database and to compare this rate with estimates from other prevalence studies.
Methods: A cohort was extracted from a group of antiepileptic drug (AED) users who met two inclusion criteria: (1) use of AED more than once and International Classification of Disease (ICD) codes indicating epilepsy or (2) use of AEDs except clonazepam for more than 90 days without ICD codes of epilepsy.
Results: In total, 559 AED users were included. The estimated crude prevalence of AED use was 0.42% of the adult population (0.4% for women and 0.45% for men), and 72% of the cohort (n=400) used only one AED.
Conclusion: Our estimate of prevalence of treated epilepsy through the NHI system has much larger coverage of population with more credible registration system, and appears to be closer to the truth than two previous small-scaled community-based studies in Taiwan.