Supplementary Material for: The Association of Poor Academic Performance with Tic Disorders: A Longitudinal, Mainstream School-Based Population Study

Background: Little is known about the academic
performance of students with tic disorders (TD). Our aim was to
investigate the association of TD and poor academic performance over
time. Methods: Longitudinal, observational study of
mainstream schoolchildren comparing grade retention (GR) and learning
disorders (LD) in students with vs. without TD between 2010 and 2014.
Students with vs. without TD based on DSM-IV-TR criteria, or with vs.
without GR and LD were compared in terms of comorbidities, school, and
environmental characteristics. The association of TD with GR was
analyzed using hazard ratios (HRs) with 95% CIs, and with LD using
logistic regression analysis [Odds ratio (OR)]. Results:
Two hundred fifty-eight students were included (mean age 14.0 ± 1.71
years, 143 [55.4%] males). The incident rate for TD and GR was 2.6 and
3.3 per 100 persons-year, respectively. LD found in 21 (9.9%) students
was associated with TD (OR 11.62, 95% CI 2.21-60.90, p = 0.004), and attention deficit hyperactivity disorder (ADHD; OR 6.63, 95% CI 1.55-28.37, p
= 0.01). Low psychological support (HRs 12.79, 95% CI 3.39-48.17) and
low sport participation (HRs 6.41, 95% CI 1.54-26.78) were risk factors
for GR. Conclusions: TD was associated with academic
difficulties, namely, LD in conjunction with ADHD but not GR. The
diagnosis of TD and comorbidities, and the initiation of proper
treatment could have a favorable impact on school performance, and
consequently on social development.

背景：目前对于抽动障碍（tic disorders, TD）学生的学业表现尚缺乏充分研究。本研究旨在探讨抽动障碍与长期学业不良之间的关联。
方法：本研究为纵向观察性研究，纳入2010至2014年间的普通在校学龄儿童，对比存在与不存在抽动障碍的学生的留级（grade retention, GR）与学习障碍（learning disorders, LD）发生情况。依据《精神障碍诊断与统计手册第四版修订版》（DSM-IV-TR）标准划分存在与不存在抽动障碍的学生，同时对比存在与不存在留级、学习障碍的学生的共病情况、学校及环境特征。采用带有95%置信区间（95% CIs）的风险比（hazard ratios, HRs）分析抽动障碍与留级的关联，采用logistic回归分析[比值比（Odds ratio, OR）]分析抽动障碍与学习障碍的关联。
结果：本研究共纳入258名学生，平均年龄为14.0±1.71岁，其中男性143名（占比55.4%）。抽动障碍与留级的发病率分别为每100人年2.6例与3.3例。21名学生（占比9.9%）存在学习障碍，其与抽动障碍存在显著关联（OR=11.62，95%CI：2.21~60.90，p=0.004），同时学习障碍与注意缺陷多动障碍（attention deficit hyperactivity disorder, ADHD）亦存在关联（OR=6.63，95%CI：1.55~28.37，p=0.01）。心理支持不足（HRs=12.79，95%CI：3.39~48.17）与体育参与度低下（HRs=6.41，95%CI：1.54~26.78）是留级的危险因素。
结论：抽动障碍与学业困难存在关联，即合并注意缺陷多动障碍的学习障碍，但与留级无显著关联。对抽动障碍及其共病进行诊断并启动规范治疗，或可对学生的学业表现乃至社会发展产生积极影响。