Secular trends and population differences in the incidence of epilepsy. A population-based study from Saskatchewan, Canada

Abstract

Purpose: To estimate the incidence of epilepsy in Saskatchewan, Canada between 2005 and 2010 by using provincial administrative health database stratifying gender, age, self-reported Registered Indian (RI) status and secular trends. Methods: An epilepsy database was created through linkage of services claims data from the provincial health database of Saskatchewan, Canada between 2005 and 2010 with a four years washout period (2001–2004). The algorithm used was at least two physician visit with the diagnosis of epilepsy on a different date within 730 days or at least one hospital separation with the diagnosis of epilepsy. Results: Between 2005 and 2010 the overall crude and age-standardized incidences of epilepsy were 63 new epilepsy patients per 100,000 person-years and 62 per 100,000 person-years respectively. The overall age-specific incidence showed a gradual increase toward a high point in elderly. The incidence rate was slightly higher in men than in women who were older than 39 years. There was a significant downward trend over time in the incidence of epilepsy from 2005 to 2010 in Saskatchewan. For self-declared RI the overall age-standardized incidence of epilepsy was 122 per 100,000 person-years. The rate ratio (RR) incidence difference between self-identified Registered Indian (RI) and non-self-identified RI was 1.6. Conclusions: The incidence of epilepsy in Saskatchewan, Canada was comparable to previous incidence studies from developed countries. This study is the first Canadian study calculating the secular trends and all-age group incidence of epilepsy and one of the few studies showing the incidence of epilepsy in a self-declared Registered Indian population.