Epilepsy prevalence by individual interview in a Norwegian community

Incomplete case finding is a problem in epidemiological studies of epilepsy. We tried to optimize case ascertainment by combining information from individual interviews and medical records. During 2 years, 1838 inhabitants of Vågå, Norway, aged 18-65 (88.6% of the target population) were interviewed as part of an epidemiological study of headache. Individuals with learning disability, mental disorders and dementia were excluded. One question concerning epilepsy was presented to 1793 consecutive cases (mean age 35, males 49%): "Have you ever had convulsions, epileptic fits or other epileptic symptoms?" The medical records of the 133 subjects who acknowledged this possibility were reviewed, and telephone interviews were performed when needed. A diagnosis of epilepsy had been made in 41 subjects. Twenty-one were treated with antiepileptic drugs, of whom 12 had had seizures within the last 5 years. By this unique method of case ascertainment, the prevalence of epilepsy in adults (cases under treatment) was 1.2%, and of active cases 0.7%, despite the fact that high-risk groups for epilepsy, such as elderly people and individuals with cognitive deficits, were excluded. Although these findings were derived from a small population in a circumscribed rural area, they suggest that the true prevalence of epilepsy may be higher than reflected in many previous studies.