Risk factors in subacute sclerosing panencephalitis: a case-control study.

Fifty-two persons with subacute sclerosing panencephalitis (SSPE) were compared with playmate and hospital controls matched for age, sex, and race. Persons with SSPE were more likely to have had measles than their age-matched controls. The age at measles infection for children with SSPE was significantly younger than that for controls who had had measles. Persons with SSPE were less likely to have received measles vaccine than were playmate or hospital controls. There were no differences with regard to the average age at vaccination, having received more than one measles vaccination, or having received measles vaccine after natural measles. Although measles vaccine may rarely predispose a child to develop SSPE, the overall impact of vaccination has been to prevent SSPE by preventing natural measles. No significant differences were observed between cases and controls for infections other than measles, or for vaccines other than measles vaccine. Previous epidemiologic studies have noted significant geographic clustering of SSPE and higher rates in children living in rural areas. These findings suggest that environmental factors other than measles are important in the pathogenesis of SSPE. In this study, children with SSPE were more likely to have suffered a serious head injury and to have come from larger families and more crowded homes than control children. Persons with SSPE were significantly more likely to have close exposure to birds (p less than 0.001) and to swine (p less than 0.05) than were control persons. No differences between cases and controls were found for exposure to other animals. These data suggest that some infectious agent(s), transmitted from birds to man, may have contributed to the development of SSPE in predisposed individuals. A variety of other factors were investigated and found not to correlate with SSPE. These included birth weight, breastfeeding, maternal age at birth, nutritional status, source of drinking water, development, and allergic or atopic disorders.