Validation of the Chinese version of Morningness-Eveningness Questionnaire for screening delayed sleep-wake phase disorder with bipolar disorder among Han Chinese population

Objective: Delayed sleep-wake phase disorder (DSWPD) is commonly seen in bipolar disorder (BD). However, valid screening tools for DSWPD have not been available, especially in China. Therefore, this study aimed to explore the validation of the Morningness-Eveningness Questionnaire (MEQ) for screening DSWPD with BD among Han Chinese population. Methods: 267 patients with bipolar disorder and 130 healthy controls were screened with the Chinese version of Morningness-Eveningness Questionnaire (MEQ) for DSWPD. Of these, 49 completed the re-test after 2 weeks. The DSWPD diagnosis was based on clinical interview with the patients and related informants by trained psychiatrists according to the diagnostic criteria of the International Classification of Sleep Disorders (3rd edition, ICSD-3). Cronbach's α coefficient, split-half reliability coefficient, and the Intra-class Correlation Coefficient (ICC) were calculated to assess the reliability of MEQ. The receiver operating characteristic curve (ROC) was plotted to evaluate MEQ performance. The optimal cut-off was chosen by maximizing the Youden index. Results: The internal consistency, split-half, and retest reliabilities of the MEQ were 0.758, 0.719, and 0.661, respectively. Three factors were obtained for the MEQ scale based on Exploratory factor analysis, with a cumulative factor loading of 37.384%. BD patients with DSWPD had significantly lower MEQ scores (36.85 ± 6.40) compared to BD patients without DSWPD (47.44 ± 7.39) and healthy controls (47.96 ± 7.28) (both p