Factors associated with newly diagnosed tic disorders among children in Taiwan: a 10-year nationwide longitudinal study.

Increased attention has been paid to tic disorders clinically, yet relatively few studies have probed potential factors that account for the occurrence of tic disorders in the general population. In this study, we used data derived from the Taiwan's National Health Insurance Research Database to examine an array of factors related to the diagnosis of tic disorders and to further probe gender heterogeneity in clinical manifestation. Poisson regression analyses were applied to model the effects of birth cohort, period, and age, separately, on tic disorders. A total of 880 newly diagnosed tic disorders were identified from 2002 to 2009 among 100,516 youngsters in the study dataset who were born between 1997 and 2005. The results showed that a significant increase in the adjusted incidence rate ratio (IRR) was observed when age increased, with the highest adjusted IRR found at age 8-9 years. Compared to the time period from 2002 to 2005, an elevated IRR was found in the time period from 2006 to 2009 (adjusted IRR: 1.37; 95% CI: 1.05-1.80). Boys tended to be more likely to receive their initial diagnosis from psychiatrists and have higher comorbid attention-deficit/hyperactivity disorder (ADHD), as compared with their girl counterparts. In conclusion, the findings indicate that the effects of age and period, respectively, influence the occurrence of newly diagnosed tic disorders. Gender difference and higher frequent comorbid ADHD in boys than in girls were observed in this study.