Validation of a three-dimensional model about sleep: habits, personal factors and environmental factors

Objectives: The present study aims to test the factor structure of two sleep questionnaires and their internal consistency in a sample of adolescents and their respective parents and to evaluate the validity and robustness of a three-dimensional model about sleep, addressing nine subcategories related to sleep habits, personal and environmental factors. Methods: Participants were 654 adolescents from Portuguese schools, who completed “My Sleep and I” questionnaire, and 664 parents who completed “My child's sleep” questionnaire; to them confirmatory factor analysis was applied. Results: Confirmatory factor analysis indicate that a nine-factor model has better fit indices compared with the others tested models for both samples (adolescents: χ2/df (Chi-square/ degrees of freedom)=2.59, Comparative Fit Index (CFI) = .82, Goodness-of-Fit Index (GFI) = .92, Root Mean Square Error of Approximation (RMSEA) = .049, Expected Cross-Validation Index (ECVI) = 1.416; Parents: χ2/df= 2.89, CFI = .85, GFI = .91, RMSEA=.053, ECVI = 1.528). Moreover, the comparison of the models through Δχ2 index (chi-square difference between rival models) indicates a better fit for this model, Δχ2 (24) = 186.5, p<.001 for adolescents and Δχ2 (24) = 209, p<.001 for parents. Also, the three second-order factors have good internal consistency, convergent and discriminant validity for all factors in both samples. Conclusions: Results postulate that the three factors and their nine subcategories account for correlations between sleep habits, self-perceptions and knowledge about sleep.