Italian validation of the Sleep Condition Indicator: A clinical screening tool to evaluate Insomnia Disorder according to DSM-5 criteria

Study objectives: The present study investigated the validity, reliability and, as novel aspects, the temporal stability and discriminant validity of the Italian version of the Sleep Condition Indicator (SCI), a new brief tool to appraise Insomnia Disorder (ID) according to the new criteria of the DSM-5.

Methods: Subjects with ID (DSM-5), Obstructive Sleep Apnea Syndrome (OSAS) (ICSD3) and a group of healthy subjects (H) were recruited. At the first evaluation (T1), SCI, the Insomnia Severity Index (ISI) and the Pittsburgh Sleep Quality Index (PSQI) were administered. ID patients also completed the SCI 2months later (T2). Statistical analyses included Cronbach's alpha co-efficient calculation, Intraclass Correlation, Receiver Operating Characteristic (ROC) curves and Pearson correlations.

Results: Eighty-eight ID (n=50 F, mean age 49.9±15.1 years), 43 OSAS (n=22 F, mean age 50.2±9.1 years) and 40 H (n=22 F, 49.3±13 years) were recruited at T1. SCI, PSQI and ISI scores were significantly higher in the ID group vs H and OSAS (both p<.001). ROC analysis revealed cut off of >18 to correctly identify 100% of H, cut off of >17 the 100% of OSAS and <17 the 100% of ID. Cronbach's alpha were 0.71 at T0, 0.78 at T2 for ID, 0.76 and 0.81 respectively for H and OSAS. SCI showed a negative correlation with ISI (p<.01) and PSQI (p<.05).

Conclusion: The Italian version of SCI shows good internal consistency, temporal stability and concurrent validity in insomnia, confirming data on the original version. Importantly, the present study shows that the SCI effectively discriminates insomnia from both normal sleep and OSAS.