Development and psychometric evaluation of the Children's Sleep-Wake Scale☆,☆☆
Introduction
This article describes the development and psychometric evaluation of the Children's Sleep-Wake Scale (CSWS), a caregiver-report measure of behavioral sleep quality in 2- to 8-year-old children. The CSWS differs from existing questionnaires designed to screen for pediatric sleep disorders or to assess childhood sleep disturbances1, 2: (a) it is a research instrument; (b) it provides data on the full range of sleep quality, from very good to very poor; and (c) it quantitatively assesses 5 distinct behavioral dimensions of sleep quality, including Going to Bed, Falling Asleep, Maintaining Sleep, Reinitiating Sleep, and Returning to Wakefulness.
A comprehensive understanding of sleep health necessitates complementary behavioral and physiological approaches.3 Polysomnography is the gold standard for quantifying multiple aspects of sleep physiology, and actigraphy provides ambulatory estimation of continuous sleep states via motor activity.4 Both, however, are costly and time/labor intensive, and do not capture all behavioral aspects of children's sleep health, such as bedtime resistance or difficulties awakening in the morning. Given the high prevalence of childhood behavioral sleep problems5, 6, 7, 8 and the need to better understand their etiology, consequences, and treatment course, questionnaires with established reliability and validity are needed.
Development of the CSWS was based on a theoretical framework (Fig. 1) that was informed by published models of infant sleep regulation and disturbance9, 10 and empirical data. This framework proposes that children's behavioral sleep quality (middle oval) occurs within the broad context (outer oval) of 2 extrinsic domains (ie, culture and physical environment) and 2 intrinsic child domains (ie, psychosocial functioning and biological/health status). Caregiver behaviors (middle oval), including sleep hygiene practices and behavioral change strategies, can mediate or moderate relationships between sleep quality and contextual domain variables. Similar to other transactional models,11 this framework assumes interactions between domains and differences in relationships between domain variables and sleep. Domain variables can also have a direct impact upon sleep quality and vice versa. Individual combinations of the domain variables influence each behavioral dimension of sleep quality. Difficulties with one or more of these behavioral dimensions can directly impact caregivers' behaviors and, thus, children's psychosocial functioning, development, and health status.
This project utilized conventional and rigorous procedures for scale development and psychometric evaluation.12, 13 Five studies with independent samples were completed. After establishing content validity of generated items, we evaluated internal consistency and refined and/or deleted items (studies 1 and 2). Study 3 examined the factor structure of the CSWS with confirmatory factor analysis (CFA), evaluated subscale-to-subscale correlations, and then reassessed internal consistency. Study 4 examined the 1-month temporal stability (test-retest reliability) of the CSWS. Finally, study 5 evaluated the construct validity of the CSWS via extreme-groups discrimination.
Section snippets
General analysis
Data were analyzed with SPSS version 11.0 (SPSS Inc, Chicago, IL) or version 20.0 (IBM Corp, Armonk, NY). Summary measures include range, %, or M ± SD. Univariate distributions of variables were evaluated for normality, and correlations were computed following inspection of scatterplots to confirm linearity and to identify potential outliers. For all analyses, the significance level was α = .05.
Preliminary CSWS development: item generation and content validity
Seep medicine and child psychology experts generated a pool of 79 items written below a sixth grade reading level (1-month reference period; 3-point response set: Rarely, Sometimes, Usually). As a first step, primary caregivers (n = 30) of 2- to 5-year-olds attending a community daycare/preschool provided qualitative feedback on the clarity of directions and items, suitability of the scaling method, and approximate time to complete administration.
Following scale revisions, 9 pediatric sleep
Study 1: Item refinement
Participants were recruited via flyers, personal contact at community events, daycares, and schools (contact information obtained on-site for subsequent follow-up by researchers), and/or snowball sampling14 from a tri-county area of southern Mississippi, as guided by the 1990 Census of Population and Housing.15 The CSWS and a general demographics and health questionnaire were completed by the primary caregiver for only one child per family using a controlled selection method.16 As approved by
Study 2: Item analysis
We used the same recruitment strategy and approach for obtaining informed consent as described above for study 1. In a new sample of 543 primary caregivers of 2- to 8-year-old children (4.9 ± 2.0 years; Supplemental Data, Table S1) contacted by telephone, 485 responded to the 50-item scale (response rate = 89%). Item analysis and selection followed the same procedure as in study 1, resulting in a total of 39 items. Cronbach α (internal consistency) for the 5 subscales was as follows: Going to
Study 3: CFA and scale characteristics
Participants were recruited face-to-face at community events, shopping malls, daycares, and schools, where they signed an institutional review board–approved consent form and completed the CSWS and a general demographics and health questionnaire. A total of 751 of 843 primary caregivers (response rate, 89%) of children aged 2 to 12 years (6.1 ± 3.1 years; Supplemental Data, Table S1) completed the 39-item CSWS.
As described in study 1, item analysis (ie, inter-item correlations and item
Study 4: Test-retest reliability
A total of 55 undergraduate primary caregivers with 2- to 8-year-old children were recruited from psychology classes and administered the 25-item pencil-and-paper version of the CSWS in the research laboratory. Of these, 36 (4.4 ± 2.1 years; Supplemental Data, Table S1) completed the 1-month retest assessment (65% completion rate). The temporal stability assessment of the CSWS showed a reliability coefficient of r = 0.85 (P < .001) for the CSWS total scale and the following subscale
Study 5: Construct validity
As a final step, we examined the extent to which CSWS subscale and total scale scores (a) converged with other assessments of sleep quality (ie, sleep diary and actigraphy) and (b) discriminated groups of children expected to differ on multiple behavioral dimensions of behavioral sleep quality.
Participants recruited via flyers at daycares, schools, and pediatric clinics made direct contact with the research team, who then provided an explanation of the study and obtained informed consent by
Correspondence between CSWS and sleep diary and actigraphy measures
As hypothesized, we found moderate correlations between CSWS subscale/total scale scores and corresponding analog diary sleep quality ratings (r = 0.58 to r = 0.72; Table 4). With regard to concordance between CSWS scores and actigraphy measures (Table 4), children with poorer success in Falling Asleep were more likely to have longer sleep onset latencies (r = 0.61). Relationships between Maintaining Sleep subscale and actigraphic sleep minutes (%) and sleep efficiency variables were positive
Acknowledgments
This work was supported by funding from the National Institute of Mental Health (F31-MH065831 to MKL). We thank the undergraduate and graduate students at the University of Southern Mississippi who assisted with data collection, as well as the numerous caregivers and children who participated in these studies.
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Work performed at: Department of Psychology, University of Southern Mississippi, USM Box 5025, Hattiesburg, MS 39406, USA.
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Conflicts of Interest: None.