Experts have confirmed it: tics are not a rare or uncommon disorder. It is the second study to be conducted in Spain to date, and the first of great importance, revealing that the prevalence of these motor disorders in the child population is 16.86%. The incidence is greater in boys than girls, and they tend to disappear or reduce with age.
"Tics are a very common disorder," explains Esther Cubo, researcher from the Yagüe de Burgos General Hospital and the new study's lead author. "Before, it was believed to be a rare condition, and since studies were only conducted for people that consulted the doctor, only severe tics were observed. Now we have noticed that most are mild disorders that do not have any functional repercussion."
Although various epidemiological studies have been conducted, this is the second in Spain, with a larger population size than the first one, which only recorded data in two school centres. This study determines the prevalence of tics in a sample of 1158 school children in the province Burgos, but the authors believe that these figures can be extrapolated to the rest of the Spanish population.
The results, published in the journal Pediatric Neurology reveal that while 16.86% of children in ordinary schools had tics, the number rose to 20.37% in special education centres. In both cases, it was more frequent in boys than girls.
Experts also analysed other related disorders, such as attention deficit disorder. Tics fluctuate and increase in situations of stress, such as family or school problems. The most severe diagnosis were chronic motor tic disorders (6.07%) and Tourette's syndrome (5.26%).
"There is still a lack of knowledge, even among medical staff, as to why diagnosing tics has to be associated with coprolalia -insults, swear words," highlights Cubo. "In fact, it is classified as being a rare disease, but we have to consider it as being common so that it is diagnosed correctly."
Tics are hereditary in neurological development during infancy, characterised by sudden repetitive and stereotyped movements and sounds, which longitudinally and gradually improves in most subjects. "It is the most common movement disorder for children and teenagers," adds the researcher.
The epidemiological studies show that as the years pass, if it does not disappear completely, it does become less intense. Tourette's syndrome, chronic phonic disorder, transitory tics and unspecified tics all have tics as a symptom.
Although the cause is still not known, experts point out that it involves an involuntary movement suppression disorder in the circuit between the basal ganglia and motor cortex. Functional neuroimaging has proven that tic sufferers have certain areas in the brain that are overactive or which do not activate correctly to suppress these involuntary movements or sounds.
Esther Cubo, José María Trejo Gabriel y Galán, Vanesa Ausín Villaverde, Sara Sáez Velasco, Vanesa Delgado Benito, Jesús Vicente Macarrón, José Cordero Guevara, Elan D. Louis, Julián Benito-León. "Prevalence of Tics in Schoolchildren in Central Spain: A Population-Based Study". Pediatric Neurology 45 (2011):100-108, August 2011.