The incidence of epilepsy and of all unprovoked seizures was determined for residents of Rochester, Minnesota U.S.A. from 1935 through 1984. Age-adjusted incidence of epilepsy was 44 per 100,000 person-years. Incidence in males was significantly higher than in females and was high in the first year of life but highest in persons aged > or = 75 years. Sixty percent of new cases had epilepsy manifested by partial seizures, and two thirds had no clearly identified antecedent. Cerebrovascular disease was the most commonly identified antecedent, accounting for 11% of cases. Neurologic deficits from birth, mental retardation and/or cerebral palsy, observed in 8% of cases, was the next most frequently identified preexisting condition. The cumulative incidence of epilepsy through age 74 years was 3.1%. The age-adjusted incidence of all unprovoked seizures was 61 per 100,000 person-years. Age- and gender-specific incidence trends were similar to those of epilepsy, but a higher proportion of cases was of unknown etiology and was characterized by generalized onset seizures. The cumulative incidence of all unprovoked seizures was 4.1% through age 74 years. With time, the incidence of epilepsy and of unprovoked seizures decreased in children and increased in the elderly.

The increased risk of seizures after traumatic brain injury varies greatly according to the severity of the injury and the time since the injury.

The prevalence of epilepsy in Rochester, Minnesota has been determined for a specific date in each of 5 decennial census years. Individuals with a diagnosis of epilepsy (recurrent unprovoked seizures) who were known to have experienced a seizure or who had received antiepileptic medication in the preceding 5 years were considered active prevalence cases. By this definition, the age-adjusted prevalence per 1,000 population, increased steadily from 2.7 in 1940 to 6.8 in 1980. At each of five prevalence dates, for all prevalence cases, 60% had epilepsy manifest by partial seizures, and 75% had no known etiology. Prevalence was higher for males than females for all except the last prevalence day. After 1950, prevalence tended to increase with advancing age and was highest in the oldest age groups. On the average, the 1980 prevalence cases had epilepsy less than 10 years and greater than 50% had their first diagnosis in the first 20 years of life.

Standardized mortality ratios (SMR) were determined for a cohort of patients with first diagnosis of epilepsy as residents of Rochester, Minnesota, between 1935 and 1974. SMR for the total group was 2.3 through 29 years of follow-up. SMR was lower for those with idiopathic epilepsy, although still significantly increased from expected. Several groups with idiopathic epilepsy did not have significantly elevated mortality rates. This included patients with absence seizures, partial and complex seizures, first diagnosis of epilepsy between ages 1 and 19, or patients who were female. Patients with febrile convulsions did not demonstrate alterations in expected mortality. Patients with single idiopathic generalized seizures did have an increase in mortality.For the group as a whole, as well as all idiopathic cases, the most significant increase in SMR occurred in the first 10 years following diagnosis. Interval SMRs were also significantly increased between 25 and 29 years following diagnosis. This suggests either a late effect associated with predisposition for seizures, an effect related to the chronic medication used for therapy, or a combination of the two. Patients experiencing remission of seizures demonstrated an increase in SMR, suggesting that factors other than seizure occurrence affect mortality. While an excess number of deaths relating to pulmonary events, accidents, extracranial neoplasms, and noncerebral or noncardiac vascular disease were observed, given the person-years of experience in this study, these generally were of borderline significance and there seemed no cause of death unique to those in the study group.

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