The epidemiology of infantile spasms

Objective: The aim of this study was to estimate population based incidence rates for infantile spasms (IS) and to study our clinical impression that the incidence of IS has recently decreased in the Canadian Provinces of Nov a Scotia and Prince Edward Island. Methods: Birth cohorts from 1978 to 1998 , identified through the hospital health records, EEG records and physician computerized databases, were followed for two years for the development of IS. Disease incidence rates were calculated using denominators derived fro m Statistics Canada's reported annual live birth rates. Results: The inclus ion criteria for IS were fulfilled by 75 patients. The overall incidence of IS was 30.7/100,000 live births (95% CI 24.3, 38.8). Etiologic classificat ion was symptomatic for 51 cases (68%), cryptogenic for 18 (24%), and idiop athic in six children (8%). Although there were more males (N=44) than fema les (N=31), the incidence rates were similar. There was a marked variabilit y in annual and five-year incidence rates. Conclusions: Although the clinic al characteristics of our patients were similar to other reported IS popula tions, the instability in IS incidence rates indicates a need for caution i n interpreting smaller IS epidemiologic studies.