Psychometric properties and population-based score distributions of the Japanese Sleep Questionnaire for Preschoolers

Reliability and validity of instruments containing reported sleep measures among children from birth to <5 years of age: A systematic review

Valid and reliable sleep measures during the early years are crucial for practitioners and researchers seeking accurate evaluation methods. The authors in this review systematically examined the psychometric properties of instruments containing reported sleep measures in children from birth to <5 years of age. The search was conducted using several electronic databases, including MEDLINE, EMBASE, PsycINFO, Web of Science, CINAHL, SPORTDiscus, Scopus and HaPI, with the most recent update on August 30, 2022. The quality of the included studies was assessed using the COSMIN methodology. A total of 79 studies were analyzed. However, none of these measures had undergone a comprehensive evaluation of all psychometric properties. Unfortunately, suitable reported sleep measures for children aged 0-4.99 years could not be identified through this review. Further research is needed to develop and validate psychometrically robust sleep assessment tools for this specific age group.

Are the Sleep-Wake Cycle and Sleep Duration Ethnically Determined? A Comparison of Tibetan and Japanese Children's Sleep

BACKGROUND

Several environmental factors affect sleep. We investigated the sleep and sleep-related habits of preschool children living in Tibet and conducted an international comparison with those in Japan.

METHODS

We conducted a community-based cross-sectional study using the Chinese version of the Japanese Sleep Questionnaire for Preschoolers (JSQ-P-C) and compared the results with previous data on Japanese children.

RESULTS

The sleep status of 3113 children aged 3-6 years old in Qinghai province was evaluated. The average wake time and bedtime of the Tibetan children were 7:20 ± 0:31 and 21:16 ± 0:43, respectively. Their mean nocturnal sleep duration was 10.0 ± 0.7 h. In comparing 3-year-old children, the time for which they viewed TV in Tibet was shorter (65.5 ± 44.6 min) than that in Japan (149.7 ± 76.6 min), and the mother's bedtime was earlier in Tibet (21:28 ± 2:14) than in Japan (23:20 ± 1:05). However, the bedtime and sleep duration of the Tibetan children (21:17 ± 0:37 and 10.0 ± 0.7 h) were fairly similar to those of the Japanese children (21:24 ± 1:57 and 9.8 ± 0.8 h).

CONCLUSIONS

The late bedtime and short nocturnal sleep duration of Tibetan toddlers were the same as those of Japanese toddlers despite considerable differences in their lifestyle and environment.

Translation and validation of the Thai Version of the Japanese Sleep Questionnaire for Preschoolers (JSQ-P)

PURPOSE

This study aimed to translate and validate the Japanese Sleep Questionnaire for Preschoolers (JSQ-P) into a Thai version and to evaluate factors associated with sleep problems in preschoolers.

METHODS

The cross-cultural adaptation of JSQ-P into Thai version of JSQ-P (TH-JSQ-P) was performed including forward translation, reconciliation, backward translation, and final approval by the original creator. Children aged 2-6 years from community and clinical settings were enrolled. The TH-JSQ-P was completed by parents of preschool children twice within 10-14 days to assess its reliability and validity. Six validity tests including face validity, content validity, structural validity, construct validity, criterion validity and predictive validity were assessed. Demographic data, Epworth sleepiness scale (ESS), medical and behavior problems, and socioeconomic status were collected for analysis.

RESULTS

A total of 2613 participants completed the TH-JSQ-P, with 1207 completing it twice to assess test-retest reliability. The TH-JSQ-P had good internal consistency reliability and test-retest ability with Cronbach's alpha value of 0.898 and intraclass correlation coefficient of 0.814. The content validity was acceptable. The ESS had correlation with sleep problems in almost all subscales except for sleep habit.

CONCLUSIONS

The TH-JSQ-P is a valid and reliable instrument for evaluating sleep problems in preschool children in Thailand. It has the potential to be extensively utilized to screen for sleep problems, thereby enabling healthcare professionals to identify them early and implement prompt management.

Sleep problems among Asian preschool children with neurodevelopmental disorders

BACKGROUND

Sleep plays an important role in children's behavior, emotional control, and cognitive development. There is a higher prevalence of sleep problems in children with neurodevelopmental disorders (NDDs) compared to those without disease. There are a few studies regarding sleep problems among Thai preschoolers with NDDs. This study examined sleep problems in preschoolers with NDDs, compared with typically developing children (TD), and studied the association between sleep problems and behavioral problems among preschoolers with NDDs.

METHODS

Sleep problems in 140 children aged 2 to 6 years with NDDs; autism spectrum disorders, attention deficit/hyperactivity disorder, global developmental delay, and developmental language disorder were evaluated by using the Thai version of Japanese Sleep Questionnaire for Preschoolers (TH-JSQ-P) and compared with 285 TD children at the same age. Behavioral problems in the NDDs group were evaluated by using the Child Behavioral Checklist (CBCL). Sleep and behavioral problem scores were analyzed by adjusted age, sex, underlying diseases, and medications used and compared between the two groups.

RESULTS

The study found that 48 % of the TD group and 71 % of the NDDs group were identified as having sleep problems. The NDDs group had significantly higher total TH-JSQ-P score and in five subscales, including obstructive sleep apnea, restless leg syndrome-motor, parasomnias, daytime behaviors, and insomnia/circadian rhythm disorders. Total TH-JSQ-P score was found to have a moderate correlation with internalizing and externalizing behavioral problems.

CONCLUSION

Findings suggest that sleep problems are more common in preschool children with NDDs than in TD children and are associated with internalizing and externalizing behavioral problems.

Oral nutritional supplementation with dietary counseling improves linear catch-up growth and health outcomes in children with or at risk of undernutrition: a randomized controlled trial

Introduction

Childhood undernutrition is associated with increased morbidity, mortality and a high socio-economic burden.

Methods

Supporting Pediatric GRowth and Health OUTcomes (SPROUT) is a randomized, controlled trial evaluating the effects of an oral nutritional supplement (ONS) with dietary counseling (DC; n = 164) compared to a DC-only group who continued consuming their habitual milk (n = 166; NCT05239208). Children aged 24-60 months who were at risk or with undernutrition, as defined by weight-for-age [WAZ] < -1 and height-for-age [HAZ] < -1 according to the WHO Growth Standards, and who also met the criterion of weight-for-height [WHZ] < 0, were enrolled in Vietnam.

Results

ONS + DC had a larger WAZ increase at day 120 (primary endpoint) vs. DC (least squares mean, LSM (SE): 0.30 (0.02) vs. 0.13 (0.02); p < 0.001), and larger improvements in all weight, BMI and weight-for-height indices at day 30 and 120 (all p < 0.01). Height gain was larger in ONS + DC in all indices, including height-for-age difference [HAD; cm: 0.56 (0.07) vs. 0.10 (0.07); p < 0.001], at day 120. ONS + DC had larger arm muscle but not arm fat indices, higher parent-rated appetite, physical activity and energy levels, longer night sleep, fewer and shorter awakenings, and better sleep quality than DC.

Conclusion

Adding ONS to DC, compared to DC-alone, improves growth in weight and height, linear catch-up growth, and health outcomes in children with or at risk of undernutrition.

Development of the Parenting Behavior Checklist to Promote Preschoolers' Sleep (PCPP)

OBJECTIVES

To develop the Parenting Behavior Checklist to Promote Preschoolers' sleep (PCPP), quantify sleep-promoting parenting behaviors for children, and examine the scale's reliability and validity.

METHODS

The PCPP was developed based on the recommendations of the ABCs of SLEEPING for children's sleep, which is strongly supported by research evidence. Its validity and reliability were evaluated using data from 140 participants. Structural validity was estimated using exploratory factor analysis (EFA) and confirmatory factor analysis (CFA), and internal consistency was evaluated by Cronbach's α. Hypothesis testing was evaluated by analyzing the correlations between each factor of the Japanese Sleep Questionnaire for Preschoolers (JSQ-P) and the PCPP.

RESULTS

Regarding structural validity, EFA was conducted because CFA showed a poor model fit. The PCPP comprised one factor and six items. The JSQ-P subfactors of insomnia or circadian rhythm sleep-wake disorders, undesirable morning symptoms and behaviors, and insufficient sleep were moderately negatively correlated with the PCPP; the subfactor of undesirable daytime behaviors related to sleep problems was weakly negatively correlated with the PCPP. Thus, the sleep-promoting parenting behaviors listed in the PCPP were associated with better sleep in children.

CONCLUSIONS

The PCPP showed sufficient reliability and validity. Future studies should use the scale to examine more effective interventions regarding sleep-promoting parental behaviors for children.

Prevalence and factors of sleep problems among Japanese children: a population-based study

Background

High prevalence of sleep problems in not only children with neurodevelopmental disorders (NDS) but also non NDS has been established. However, there are few studies that have looked into population-based and age-specific prevalence of sleep problems of children. Moreover, there are even fewer studies that have investigated the correlation of demographic and lifestyle-related factors affecting sleep problems in children. Considering these, the purpose of this study is to assess the correlation of the prevalence of sleep problems and selected socio-demographic and lifestyle-related factors in 5-year-old Japanese children in population-based study.

Methods

Study children (SC) were recruited from two cohorts of the Hirosaki City 5-Year-Old Child Developmental Health Checkup Study. The first cohort consisted of 281 (162 males, 119 females) children recruited from 2014 to 2015, and the second cohort consisted of 2055 (1,068 males, 987 females) children from 2018 to 2019. In total there were 2,336 SC participants (1,230 males and 1,106 females). To determine the prevalence of sleep problems the Japanese Sleep Questionnaire for Preschoolers (JSQ-P) was utilized, and sleep problems are defined by a total score of ≥86. To determine socio-demographic and lifestyle-related factors affecting sleep, 10 factors (NDS diagnosis, birth month, childcare place, income, number of siblings, bedtime, waking time, sleeping hours, sleep onset delay, and screen time) were selected. Finally, to determine the correlation between prevalence of sleep problems and the selected demographic and lifestyle-related factors, data was analyzed using chi-square test.

Results

The prevalence rate of sleep problems in 5-year-olds was 18% (369/2,055). Further, the prevalence of sleep problems was high in participants with ASD (50.4%), ADHD (39.8%), <2 million yen of income (30.5%), no siblings (24.2%), >22:00 of bedtime (30.7%), >7:30 of waking time (30.7%), <9 h of sleeping hours (25.3%), >30 min of sleep onset delay (35.3%), and ≥2 h of screen time (21.1%).

Conclusion

The findings report 18% prevalence rate of sleep problems in 5-year-old children. Further, the findings establish a significant correlation of sleep problems and NDS, specific socio-demographic, and lifestyle-related factors. In considering the identified modifiable lifestyle-related factors contributing to sleep problems among the participants (i.e., bed/waking times and screen times), sleep programs to address these concerns are suggested.

Qualitative study of the association between psychosocial health and physical activity/sleep quality in toddlers

Physical activity and sleep are important factors of mental and physical health in children, with some reports indicating that their effects can persist into adulthood. However, there is limited research on the qualitative aspects of physical activity and sleep in preschool children, particularly in those aged < 3 years. Therefore, to elucidate the association between psychosocial health and physical activity/sleep in early childhood in terms of qualitative aspects, we conducted a retrospective cohort study in 2985 3-year-old children (37.2 ± 0.75 months) in Shanghai, China. An analysis using structural equation modeling indicated that current physical activity had a direct and moderate impact on current psychosocial health evaluated using the Strength and Difficulties Questionnaire. In particular, past physical activity had an indirect and mild effect on current psychosocial health via current physical activity in girls. However, regardless of sex, past sleep quality had slight impact on current psychosocial health, not only indirectly via current sleep quality, but also directly. These findings highlight the importance of considering the qualitative aspects of physical activity and sleep quality as significant factors influencing the current and future psychosocial health of children, even at a very early age (< 3 years).

Exploring role of sleep aids in sleep problems in preschool children

It is well known that children use sleep aids, such as blankets or soft toys, at bedtime. However, there is a lack of understanding regarding the factors associated with their use and role in addressing sleep problems. This study investigated 96 Japanese children aged 40 to 47 months to examine these associations. We measured children's stress (through a questionnaire and salivary cortisol [cortisol awakening response]), anxiety symptoms, behavioral problems, and temperament, and created a model to predict the status of sleep aid use. Furthermore, we explored the association between sleep aid use and children's sleep problems as evaluated by their caregivers. We found that children who used sleep aids were more likely to experience anxiety symptoms. Moreover, most children used sleep aids even when they co-slept with their caregivers and/or siblings. Their use was not uniquely associated with sleep problems. These findings suggest that sleep aid serves as a defense against anxiety, including that caused by the absence of a caregiver, rather than as a substitute for a caregiver. Our study sheds light on their role and emphasizes the importance of viewing development within the complex interactive processes of humans and objects.

The Japanese Sleep Questionnaire for preschoolers within a Malaysian context

BACKGROUND

Childhood sleep practices impact growth, development, and long-term health. There is a paucity of sleep data pertaining to preschool children in Asia, especially South-East Asia.

METHODS

This cross-sectional study involved parents of well siblings, aged 2-6 years. It aimed to: (i) test the reliability of the English version of the Japanese Sleep Questionnaire for Preschoolers (JSQ-P), and (ii) obtain the prevalence, as well as describe, sleep-related issues. Ninety-one (91) parents (74.7%; mothers) self-administered the questionnaire in the pediatric clinic waiting area of a Malaysian tertiary hospital. Recruitment was from August to November 2020.

RESULTS

The English version of the JSQ-P has good internal consistency (Cronbach alpha = 0.85). Range of Cronbach alpha values for each item: 0.36-0.87. Many (77%) children slept at 10:00 p.m. or later, similar to parents' late bedtimes. One-third had difficulty waking up in the morning. There were significant strong positive correlations between some features of restless leg syndrome, daytime tiredness, morning symptoms, and obstructive sleep apnea symptoms. Co-sleeping was prevalent (97.9%). Mean screen time for those who had set time limits was 2.35 ± 1.68 h.

CONCLUSIONS

The English-language translation of the JSQ-P is a questionnaire with good internal consistency that can be used in non-Japanese speaking countries. Parents need to be educated on healthy sleep and screen time practices to optimize children's sleep quality and quantity.

Low threshold to Vestibular and Oral Sensory stimuli might affect quality of sleep among children with autism spectrum disorder

AIMS

The current study aimed to validate the relationship between sensory characteristics and sleep dynamics among children with autism spectrum disorder (ASD) using an actigraph, which is an objective assessment device used for sleep monitoring.

METHODS

A total of 40 children (age range, 3-6 years) participated in this study (n = 20, with ASD and n = 20, age-matched children with typical development [TD]). We examined sleep dynamics using actigraph for 7 consecutive days, and the relationship between sleep parameters and sensory characteristics was analyzed using the Japanese Version of Sensory Profile (SP-J).

RESULTS

Significant differences were observed in terms of activities per minute during sleep (p = 0.02), sleep efficiency (SE) (p = 0.005), and wake after sleep onset (WASO) (p = 0.02) between the two groups. In the ASD group, significant positive correlations were observed between activities per minute during sleep and low thresholds for Vestibular Sensory stimuli (p = 0.046) and Oral Sensory stimuli (p = 0.006) using the SP-J. Based on a multiple regression analysis, the activities per minute during sleep were associated with low thresholds for Oral Sensory stimuli (β = 0.51, t = 2.29, p = 0.03), but not with other factors, in the ASD group.

CONCLUSIONS

The current study showed that atypical Vestibular and Oral Sensory modulation may be a risk indicator for high activities during sleep among preschool children with ASD. Thus, whether the interventions for these sensory characteristics are effective in improving sleep quality, daytime activities, behaviors, and cognitive functions in this group of children must be considered.

An Interactive Smartphone App, Nenne Navi, for Improving Children's Sleep: Pilot Usability Study

BACKGROUND

Healthy sleep is important not only for physical health but also for brain development in children. Several reports have revealed that Japanese adults and children have later bedtimes and shorter sleep durations compared with those in other countries, possibly because of Japanese culture and lifestyles. Therefore, an intervention tool that is suitable to the Japanese sociocultural environment is urgently needed to improve children's sleep problems in their early years.

OBJECTIVE

To provide appropriate sleep health literacy to caregivers and change their parenting behavior, we developed a smartphone app that allows reciprocal interaction between caregivers and pediatric sleep experts. This paper describes a preliminary study to examine the app's basic design and functions and to establish its acceptability and usability in a small sample.

METHODS

A total of 10 caregivers and 10 infants (aged 18-28 months; 4/10, 40% boys) living in Japan participated in the study. At the start of the trial, the e-learning content regarding sleep health literacy was delivered via a smartphone. Thereafter, caregivers manually inputted recorded data about their own and their infant's sleep habits for 8 consecutive days per month for 2 months. After pediatric sleep experts retrieved this information from the Osaka University server, they specified the problems and provided multiple sleep habit improvement suggestions to caregivers. Caregivers then selected one of the feasible pieces of advice to practice and reported their child's sleep-related behaviors via the app. Actigraphy was used to monitor children's sleep behaviors objectively. The concordance between the information provided by caregivers and the actigraphy data was assessed. The acceptability and usability of the app were evaluated using self-report questionnaires completed by caregivers; qualitative feedback was obtained via semistructured interviews after the intervention.

RESULTS

There was no significant difference between the information provided by the caregivers and the actigraphy data for bedtimes and wake-up times (P=.13 to P=.97). However, there was a difference between the actigraphy data and the caregivers' reports of nighttime sleep duration and nighttime awakenings (P<.001 each), similar to prior findings. User feedback showed that 6 and 5 of the 10 caregivers rated the app easy to understand and easy to continue to use, respectively. Additionally, 6 of the 10 caregivers rated the app's operativity as satisfactory. Although this was a short-term trial, children's sleep habits, caregivers' sleep health consciousness, and parenting behaviors improved to some extent.

CONCLUSIONS

The present findings suggest that the app can easily be used and is acceptable by Japanese caregivers. Given the user feedback, the app has the potential to improve children's sleep habits by sending individualized advice that fits families' backgrounds and home lives. Further studies are needed to confirm the efficacy of the app and facilitate social implementation.

Pediatric Sleep Tools: An Updated Literature Review

Since a thorough review in 2011 by Spruyt, into the integral pitfalls of pediatric questionnaires in sleep, sleep researchers worldwide have further evaluated many existing tools. This systematic review aims to comprehensively evaluate and summarize the tools currently in circulation and provide recommendations for potential evolving avenues of pediatric sleep interest. 144 "tool"-studies (70 tools) have been published aiming at investigating sleep in primarily 6-18 years old per parental report. Although 27 new tools were discovered, most of the studies translated or evaluated the psychometric properties of existing tools. Some form of normative values has been established in 18 studies. More than half of the tools queried general sleep problems. Extra efforts in tool development are still needed for tools that assess children outside the 6-to-12-year-old age range, as well as for tools examining sleep-related aspects beyond sleep problems/disorders. Especially assessing the validity of tools has been pursued vis-à-vis fulfillment of psychometric criteria. While the Spruyt et al. review provided a rigorous step-by-step guide into the development and validation of such tools, a pattern of steps continue to be overlooked. As these instruments are potentially valuable in assisting in the development of a clinical diagnosis into pediatric sleep pathologies, it is required that while they are primary subjective measures, they behave as objective measures. More tools for specific populations (e.g., in terms of ages, developmental disabilities, and sleep pathologies) are still needed.

Effects of Lactoferrin on Sleep Conditions in Children Aged 12-32 Months: A Preliminary, Randomized, Double-Blind, Placebo-Controlled Trial

PURPOSE

To investigate preliminarily the effect of lactoferrin (LF)-fortified formula on sleep conditions in children.

STUDY DESIGN

A preliminary, randomized, double-blind, placebo-controlled trial.

METHODS

Healthy children between the ages of 12 and 32 months who attended nursery schools in Japan were divided into two groups and assigned a placebo or LF (48 mg/day)-fortified formula. Children's sleep conditions were investigated before and after the 13-week intervention using the Japanese Sleep Questionnaire for Preschoolers (JSQ-P).

RESULTS

Altogether, 109 participants were randomized. Eight participants were eliminated due to lost to follow-up, withdrawal of consent, and ineligibility, with 101 participants (placebo, n = 48; LF, n = 53) included in the full analysis set (FAS) and used for analysis. Wake-up time, bedtime, and nighttime sleep were comparable between the two groups before and after intervention. The change in total JSQ-P T scores tended to improve in the LF group (placebo vs LF: 0.5 ± 6.5 vs -1.9 ± 6.1, p = 0.074), in particular, morning symptoms significantly improved (grumpy in the morning, hard to wake-up, and hard to get out of bed) (placebo vs LF: 0.8 ± 6.2 vs -1.9 ± 6.2, p = 0.028). A better trend was also observed in the LF group regarding restless legs syndrome (RLS)-motor (rubs feet at night and touches feet at night) (placebo vs LF: 2.3 ± 10.7 vs -0.6 ± 13.5, p = 0.083) and insufficient sleep (stays up more than one hour later the day before a holiday and wakes up more than one hour later on a holiday) (placebo vs LF: 0.1 ± 9.8 vs -1.7 ± 8.8, p = 0.095). No adverse drug reactions were found.

CONCLUSION

LF intake may improve sleep condition, especially morning symptoms in children above one year of age.

Atypical body movements during night in young children with autism spectrum disorder: a pilot study

Children with autism spectrum disorder (ASD) reportedly suffer from sleep problems at a higher rate than typically developing (TD) children. Several previous studies have reported differences in sleep indices (e.g., sleep latency) in children with ASD. However, no previous studies have focused specifically on the time course of body movements. In the present study, we investigated the time course of body movements in young TD children and young children with ASD as well as the relationship between body movements during night and social ability. Seventeen TD children and 17 children with ASD participated in this study (5 to 8 years old). We used an accelerometer attached to the waist to record movements during night and measured the average time course of body movements for 3 nights. Our results demonstrated that the rate of body movement 2 to 3 hours after the onset of body stillness was higher in children with ASD than in TD children. In addition, the higher rate of body movement at 0.5 to 1 hour after the onset of body stillness was associated with a lower social ability in the children with ASD. Our results suggested that the time course of body movements is an objective behavioural index for young children with ASD.

Prevalence of childhood obstructive sleep apnea syndrome and its role in daytime sleepiness

Objectives

To investigate childhood obstructive sleep apnea syndrome (OSAS) and its role in daytime sleepiness among school-age children.

Methods

A questionnaire survey was conducted with 25,211 children aged 6–15 (mean, 10.39) years attending 148 elementary and 71 middle schools in 10 prefectures across Japan and their parents. Questions concerned 4 sleep habit items (bedtime, sleep onset latency, wake time after sleep onset, wake-up time) and 4 sleep disorder items (loud snoring, snorts/gasps, breathing pauses, seems very sleepy in the daytime). Total sleep time (TST) was calculated with sleep habits. Severe possible OSAS (p-OSAS) was defined as having loud snoring, snorts and gasps, or breathing pauses “frequently” (≥ 5 times per week), and mild p-OSAS was rated as having any of these “sometimes” (2–4 times per week). Severe daytime sleepiness was defined as seeming very sleepy “frequently” and mild daytime sleepiness as seeming very sleepy “sometimes”.

Results

Mean prevalence of mild to severe p-OSAS and severe p-OSAS in children across all grade levels was 9.5% and 1.6%, respectively. p-OSAS was particularly prevalent in children at lower elementary levels, decreasing with advancing grade levels. Prevalence of mild and severe daytime sleepiness was 6.1% and 0.9%, respectively, among all children (7.0%). Prevalence of daytime sleepiness increased with advancing grade levels, particularly in middle-school level. Average TST was 8.4 ± 2.2 h in both elementary and middle-school levels, and decreased as grades advanced, particularly in middle-school levels. Multivariate logistic regression analysis showed that middle-school level, TST < 8 h, and p-OSAS were independent factors for daytime sleepiness. Strong correlations were found between severe daytime sleepiness and severe p-OSAS or TST < 6 h, and between daytime sleepiness and loud snoring or breathing pauses.

Conclusion

p-OSAS may be an independent factor influencing daytime sleepiness in school-age children. Loud snoring and breathing pauses could be clinical markers for children with severe daytime sleepiness.

Japanese Sleep Questionnaire for Elementary Schoolers (JSQ-ES): validation and population-based score distribution

OBJECTIVE

The Japanese Sleep Questionnaire for Elementary Schoolers (JSQ-ES) was developed to measure the sleep habits and disturbances of Japanese children. The current study aimed to present psychometric properties and describe the score distribution of the JSQ-ES. In addition, it examined correlations between the sleep and daytime behavior of school-aged children.

METHOD

Guardians of 4369 elementary school children and 100 children diagnosed with sleep disorders in two clinics completed the JSQ-ES.

RESULTS

Exploratory factor analysis and confirmatory factor analysis suggested a nine-factor structure. The JSQ-ES internal consistency was 0.876 and 0.907 for the community and clinical groups, respectively. Score distribution differences were observed between the two groups. A cut-off point of 80 was identified for the total JSQ-ES score.

CONCLUSIONS

Exploratory factor analysis and confirmatory factor analysis suggested a nine-factor structure: (1) restless legs syndrome; (2) sleep-disordered breathing; (3) morning symptoms; (4) nighttime awakenings; (5) insomnia; (6) excessive daytime sleepiness; (7) daytime behavior; (8) sleep habits; and (9) irregular/delayed sleep phase. The study verified that the JSQ-ES is a valid and reliable instrument with which to evaluate Japanese sleep habits using a large population-based sample. The JSQ-ES may be useful in both clinical and academic settings.