<b>Psychometric Evaluation of the Insomnia Severity Index in 570,295 Chinese Adolescents: A Bifactor Item Response Theory Analysis</b>

Insomnia is a prevalent and significant issue among adolescents, yet its accurate measurement remains challenging. The Insomnia Severity Index (ISI), a widely used self-report measure for assessing insomnia symptoms, lacks well-established factor structure and psychometric properties in Chinese adolescents. To address this gap, our study employed bifactor modeling and item response theory (IRT) to explore the dimensionality and reliability of the ISI in a large sample of 572,095 Chinese adolescents. Factor Structure Investigation:We tested five alternative factor models using confirmatory factor analysis (CFA).The best-fitting model was a three-factor structure with three correlated factors.However, bifactor CFA revealed that a bifactor two-factor model, excluding item 4, exhibited superior fit indices and accounted for more common variance in the ISI items.Reliability and Discrimination:Based on the bifactor two-factor model, we employed bifactor multidimensional IRT (MIRT) to assess item parameters and the test information function of the ISI.The results indicated that the ISI demonstrated high reliability and discrimination for measuring individuals with average to high levels of insomnia severity.However, its reliability and discrimination were lower when assessing individuals with very low or very high levels of insomnia severity.Implications:These findings have important implications for the measurement and diagnosis of insomnia in Chinese adolescents.Researchers and clinicians should consider the specific context and severity levels when utilizing the ISI in this population.In summary, the ISI proves to be a reliable and valid measure for assessing insomnia severity in Chinese adolescents, but its performance varies across different severity levels. Future research should explore additional factors influencing insomnia and refine measurement tools accordingly.失眠症在青少年群体中是一种普遍且影响深远的健康问题，但其精准评估仍存在诸多挑战。失眠严重指数量表（Insomnia Severity Index, ISI）是目前广泛使用的自评式失眠症状评估工具，但针对中国青少年群体，其因子结构与心理测量学特性尚未得到充分验证。为填补这一研究空白，本研究采用双因子建模与项目反应理论（Item Response Theory, IRT），针对572095名中国青少年组成的大样本队列，探究了ISI的维度结构与信效度。 因子结构探究：本研究通过验证性因子分析（Confirmatory Factor Analysis, CFA）对五种备选因子模型进行了检验。拟合效果最优的模型为包含三个相关因子的三因子结构。然而双因子验证性因子分析结果显示，剔除第4题后的双因子模型拥有更优异的拟合指标，且能够解释ISI条目更多的共同方差。 信度与区分度分析：基于上述剔除第4题的双因子模型，本研究采用双因子多维项目反应理论（Multidimensional Item Response Theory, MIRT）对ISI的项目参数与测验信息函数进行了评估。结果表明，ISI在评估中度至重度失眠症状的群体时展现出较高的信度与区分度；但在评估失眠程度极低或极高的群体时，其信度与区分度表现欠佳。 应用启示：本研究结果对中国青少年群体的失眠评估与临床诊断具有重要指导意义。研究人员与临床工作者在该群体中使用ISI时，需结合具体情境与失眠严重程度等级进行综合考量。综上，失眠严重指数量表可作为评估中国青少年失眠严重程度的可靠且有效的工具，但其性能会随失眠严重程度的不同而产生差异。未来研究可进一步探究影响青少年失眠的其他相关因素，并据此对评估工具进行优化完善。