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    • Models that can both explain and evaluate sleep

    2018-11-15

    Models that can both explain and evaluate sleep, while being usable in sleep education strategies are lacking [34]. These models are often based on sleep questionnaires. In the evaluation of sleep, questionnaires are a valid method to track sleep disturbances and can be used as reliable tools in daily clinical practice, if properly validated for the target Immunology Compound Library [32]. The existence of questionnaires for parents and children is an approach in the family context, providing important and innovative contributions towards an improved characterization of the children׳s sleep, while raising parents׳ awareness.
    Materials and methods
    Results The proposed model (PM) had values of fit indices near of those used as cut-off point. As can be seen in Table 1, PM and the nine-factor model (AM3) have better fit indices compared with the other tested models, for both samples (adolescents and parents). The comparison of the models through Δχ2 index indicates a better fit for AM3 compared with the proposed model, Δχ2(24)=186.5, p<.001 for adolescents and Δχ2(24)=209, p<.001 for parents. Chi-square differences indicate that PM had better fit compared to the other alternative models in both samples, excluding the parents׳ sample, where the AM4 and the PM do not differ significantly. Taking into account the lower internal consistency of the nine factors, indices of internal consistency, convergent and discriminant validity were computed for the three second-order factors. All indices are presented in Table 2. CR indices indicate a good reliability for all factors in both samples. Indices of convergent validity indicate that the three factors have a good convergence validity in both samples (AVE greater than .50 and less than CR). Moreover, for the adolescents׳ sample, all the three factors presented discriminant validity (AVE values are greater than MSV and ASV); in the parents׳ sample, the factors sleep habits and personal factors have a lack of discriminant validity (AVE values are greater or equal to ASV but less than MSV). Thus, Fig. 1 shows the results of the confirmatory factor analysis of the PM (three second-order factors and nine first-order factors), for adolescents and for parents, considering the values of the standardized factor weights and the individual reliability of each item of the model. The estimated regression coefficients for this model, in both samples, are high for all components, and have statistical significance (p<.001). The coefficients of the error variances and the latent variables are also moderate and statistically significant (p<.001).
    Discussion This study examined various factor structures of the questionnaires “My sleep and I” for adolescents and “My children׳s sleep” for parents, where the relative fit of a model with three second-order factors and nine first-order factors (PM), a one-factor latent model with all items (M1), a three-factor model in accordance with the three second-order factors (M2), a nine-factor model based in the subcategories from each second-order factors (M3), and a two second-order model (sleep habits and personal factors (individual aspects) and the other by environmental factors) with nine first-order factors (M4), were compared. We chose a confirmatory approach, rather than an exploratory factor analysis, based in our hypothesis about the factor structure of both questionnaires. As mentioned by Furr [13], a CFA is useful when researchers have clear (or competing) hypotheses about a scale – the number of factors or dimensions underlying its items, the links between specific items and specific factors, and the association between factors. Both the three second-order factors and nine first-order factors model (PM) and the nine-factor model based in the subcategories from each second-order factors (AM3) provided a good fit to the data, in the adolescents and parents samples. However, considering the lower internal consistency of the nine factors model, we agreed that the three second-order factors and nine first-order factors model (PM) represented better the adolescents׳ and parents׳ perceptions about sleep. We used the CR instead Cronbach׳s alpha because this has a tendency to over- or under-estimate scale reliability, and therefore CR is now preferred and may lead to higher estimates of true reliability [14].