Sleep Beliefs Scale (SBS) and circadian typology.

The aim of this work was to present the Sleep Beliefs Scale (SBS), a 20-item reviewed version of the Sleep Hygiene Awareness by Lacks and Rotert. We also examined for the first time the influence of circadian typology in sleep beliefs. Voluntary and unpaid psychology students participated in the study (n = 510; 182 men and 328 women), from Italy and Spain, aged between 18 and 33 (22.80 +/- 4.14 years). The mean score of SBS was 13.05 (SD = 3.46; range 2-20) in the total sample, with a distribution positive skewness to high score (correct beliefs) (Z = 1.82; P = 0.003). The internal consistency was good (Cronbach's alpha = 0.714) and factor analysis extracted three factors labelled 'Sleep-incompatible behaviours' (eight items), 'Sleep-wake cycle behaviours' (seven items) and 'Thoughts and attitudes to sleep' (five items). Circadian typology influences the total score and that of the three factors, as well the majority of the items that compose the SBS. The morning-type showed the best scores, the evening-type the worst, and the neither-type the medium scores. Moreover, in the men sample, the differences between circadian typology groups were higher than in the women sample. The SBS showed good psychometric properties; however, further studies in other countries, with clinical and non-student samples, and more aged subjects are needed so as to validate this psychometric instrument. The circadian typology is an individual difference that presented significant relationships with the sleep beliefs, the possibility of the evening-type being a risk factor for a worse sleep hygiene, and the maintenance of sleep problems such as insomnia may all be investigated in depth in future research.