Prevalence of tic disorders among primary school students in the city of Pavia, Italy.

BACKGROUND The prevalence of tic disorders in children varies from 1% to 29% depending on the characteristics of the study population, the diagnostic criteria, and the study design and methods. AIMS To calculate the prevalence of tic disorders among primary school children in Italy. METHODS The study population comprised 2347 primary school children from the city of Pavia (pop. 80 073), Northern Italy. Using trained school teachers as the source of cases, all children with motor or vocal tics occurring intermittently and unpredictably out of a background of normal motor activity were accepted. The type, frequency, and circumstances of tic disorders were noted. School performance was correlated to the presence of tics. RESULTS A total of 68 children (56 boys, 12 girls) aged 6-11 years were identified with tic disorders. The period prevalence was 2.9% (95% CI 2.3 to 3.7). The prevalence was 4.4% in boys and 1.1% in girls, with no detectable trends at age 6-11. Motor tics were present in 46 cases, vocal tics in 6, and motor and vocal tics in 16. Situation related tics were noted in 37 cases. A significant correlation was found between the presence of tic disorders and impaired school performance. DISCUSSIONS Tic disorders are a fairly uncommon but disabling clinical disorder among primary school children from an urban community. The fairly low prevalence of this clinical condition, as compared to other reports, can be explained by the choice of stringent diagnostic criteria and the exclusion of patients with other movement disorders.