The incidence, causes, and secular trends of head trauma in Olmsted County, Minnesota, 1935-1974.

Records in the Mayo Clinic linkage system were reviewed to determine the incidence of head trauma in Olmsted County, Minnesota, from 1935-1974. Minimum criteria for inclusion--loss of consciousness, posttraumatic amnesia, or skull fracture--were met by 3587 cases. During the decade from 1965-1974, the age-adjusted incidence rates per 100,000 population were 270 in males and 116 in females. The rate was highest--658--in males aged 15 to 24, but it was at least 50 in all age and sex groups. Major causes of head injury were automobile accidents (37%) and falls (29%). The incidence of head injuries related to automobiles and recreation has been increasing, whereas most other categories have remained stable or have declined. Of all cases, 446 were fatal, the average annual incidence being 32 per 100,000 in males and 9 per 100,000 in females. Among the groups at high risk of head trauma are those who have had head trauma previously.