Seizure Disorders: The Changes With Age

Studies of the population of Rochester, Minnesota, have provided the only data on temporal trends for the incidence of stroke in North America. Among the residents of Rochester, the average annual incidence rate of stroke declined by 46%, from 213 to 115 per 100,000 population, between 1950-1954 and 1975-1979. The decline occurred in all age and sex groups, but it occurred earlier in women than in men. The rates stabilized in the 1970s, and did so earlier in women. For 1980-1984, the incidence rate of stroke was 17% higher than that for 1975-1979. The onset of the decline in incidence rates coincided with the introduction of effective antihypertensive therapy, but stabilized and increased rates were associated with continuing improvement in the control of hypertension. The increase in the incidence rates of stroke coincided with the introduction of computed tomography, which appeared to increase the detection of less severe strokes.

We identified all diagnosed cases of infections of the central nervous system (CNS), excluding poliomyelitis, in the population of Olmsted County, Minnesota, from 1950 to 1981 and described incidence, time trends, etiologic agents, and mortality for these infections. The adjusted incidence rate for bacterial meningitis was 8.6/100,000 person-years (with a case fatality ratio of 10%) and was highest in children less than five years of age; in this age-group, rates more than doubled from 1950 to 1981. The adjusted incidence rate of brain abscess was 1.1, with a case fatality ratio of 37%. The adjusted incidence rate of aseptic meningitis was 10.9/100,000 person-years. Age-specific rates were highest in children less than one year of age and in men, and increased during the study period. The adjusted incidence rate of viral encephalitis was 7.4, with a case fatality ratio of 3.8%. Rates were highest in children less than 10 years of age and in men. By 10 years of age, 0.9% of the men and 0.7% of the women were affected by a CNS infection. Cumulative incidence (risk) through age 80 was 2.3% for men and 1.5% for women.