Prevalence of central nervous system diseases--a large retrospective cohort study of adolescents.

At age sixteen, most Israeli nationals must undergo medical evaluation for compulsory military duty. All potential conscripts are referred to the Israel Defense Forces (IDF) recruiting office. Therefore, medical screening of a vast number of adolescents is performed, offering a unique opportunity to study the prevalence of neurological diseases in an entire age cohort. Hence, screening is not affected by diagnostic or methodological bias. We performed a retrospective neuroepidemiological large cohort study of adolescents from the database of the Israel Defense Forces recruiting office during the years 1998-2002. The survey included 409 492 adolescents, among them 162 079 (39.5%) females. The most prevalent diagnoses were: headache (754 per 10 000 adolescents), permanent brain damage (197 per 10 000), epilepsy (167 per 10 000) and movement and coordination disorders (36 per 10 000). These were followed by cranial nerve disorders, sleep disorders, cranio-spinal bone defects, and chronic progressive CNS disorders. The relative risk for male adolescents within the specific disease groups was higher for movement-coordination, sleep and cranial nerve disorders. Multivariate analysis revealed gender and severity prevalence and sex-grade, or year-grade interactions in the distinct groups of diseases. This study provides important information on the prevalence of neurological diseases in adolescents and demonstrates some significant epidemiological trends.