Changes in skin cancer morbidity between 1971-72 and 1977-78.

Skin cancer incidence rates for two geographic areas of the United States were analyzed for detection of significant changes in risk over a 6-year period (1971-72 to 1977-78). Changes in rates were examined by cell type, anatomic site, sex, and age. In general risk has increased, but the size of the increase varied by cell type, sex, and anatomic site. Statistically significant increases were limited to tumors of the basal type. The risk of basal cell skin cancer appears to have increased about 18% or almost 3% per year. Increases did not depend on age group. Among males the increases were most notable for sites other than face, head, and neck, whereas among females the increases were not associated with site.