The Dysfunctional Beliefs and Attitudes about Sleep scale: Dimensions of the European Portuguese DBAS-30 and development of a new short version (DBAS-SF-16).

OBJECTIVES: The Dysfunctional Beliefs and Attitudes about Sleep Scale (DBAS) is the most widely validated instrument for assessing sleep-related cognitions. This study aimed to examine the reliability of the DBAS-30 European Portuguese version, explore its dimensionality, and develop a new short version suitable for differentiating the presence/absence of insomnia.

METHODS: From 824 participants aged 18-85 years, the Insomnia Group (IG, n = 355, 261 females and 94 males) and Normal Sleepers Group (NSG, n = 292, 237 females, 54 males and 1 with no response) were constituted. Thirty-one patients with Obstructive Sleep Apnea Syndrome were also recruited. For the DBAS 16-items version, the ability to differentiate dysfunctional beliefs between people with and without insomnia was used as the main criterion for item retention.

RESULTS: DBAS-30 PT demonstrated good internal consistency and significantly discriminated IG from NSG. Based on a robust EFA (RDWLS), a three-dimensional structure was determined for IG (Ageing and Hopelessness, Sleep Expectations, and Consequences and Helplessness). DBAS-SF-16 presented as an internally-consistent measure with a reliable two-factor structure (Consequences and Helplessness, Medication and Hopelessness) and showed construct and known groups validity. ROC analysis demonstrated DBAS-SF-16's relevant clinical accuracy, and 4.3 provides the best cut-off score in detecting the level of dysfunctional beliefs associated with clinical insomnia.

CONCLUSIONS: A new and meaningful dimensionality of the DBAS-30 was found. DBAS-SF-16 showed to be a reliable, valid, and robust tool for evaluating dysfunctional beliefs about insomnia in clinical and non-clinical populations.