Background
Several cross-sectional studies show that restoring sleep is significantly associated with daytime functioning in terms of favorable cognitive, emotional, behavioral, and social processes. This holds true for infants and toddlers [
1‐
4], preschoolers [
5,
6], children [
7‐
12], and adolescents [
12,
13]. Longitudinal studies further suggest that poor sleep predicts unfavorable cognitive-emotional, social and behavioral patterns in later life [
13‐
20]. As regards adolescents, research showed that approximately half (45%) of 11–17-year-olds report a sleep problem for at least several nights a week, including difficulty in falling asleep, maintaining sleep stability and waking up early [
21]. Not surprisingly, inadequate sleep or inappropriate sleep quality among adolescents are associated with academic [
22] and psychological performance problems [
23,
24], obesity [
25], prehypertension [
26] and motor vehicle accidents [
27].
Scholars have further highlighted that adolescence is a period of vulnerability for the onset of sleep problems [
28]. While it is agreed that adolescents still need 8 to 10 h of sleep per night for optimal daytime functioning, a large portion of adolescents do not accomplish these standards [
28‐
30], which is usually attributed to an interplay between biological, social and behavioral risk factors [
28,
29]. For instance, biological changes association with puberty and maturation include circadian and homeostatic components of sleep, which influence the sleep-wake cycle, as well as sleep timing, sleep duration, and sleep architecture [
30,
31]. Typically, there is a shift of biological sleep patterns during adolescence toward later bedtimes and waking times, which may lead to a greater gap between sleep duration on school-nights and on weekend-nights [
32,
33]. Although there is still overlap between sleep pattern of parents and their offspring [
34‐
36], the above pattern may be reinforced by the efforts of teenagers to become more independent form their parents and to decide more freely about social/leisure activities and bedtimes [
37]. Based on the findings of a recent systematic review, Becker et al. [
38] underscored the importance of the intra-individual variability of sleep/wake patterns in adolescents, and claimed that both basic and clinical sleep recommendations should not only focus on overall sleep duration and sleep habits, but also address the stability of sleep duration and timing. Additionally, previous studies showed that during adolescence, youngsters tend to increase their screen time [
39], light exposure at night [
40], engage in more evening activities [
41], and are more likely to engage in risk behaviors [
42], which in turn may have a detrimental impact on adolescents’ sleep [
43]. Thus, poor sleep hygiene practices can be seen as potentially modifiable risk factor that may moderate some of the above-mentioned influences on adolescents’ sleep.
In this view, respecting sleep hygiene rules is an easy and cost-effective means to both maintain or re-install regular intra-individual sleep patterns. Specifically, sleep hygiene principles are defined as behavioral methods that promote sleep quality, adequate sleep time and complete consciousness during waking hours in a day [
44]. Following LeBourgeois et al. [
44], these practices include avoiding late-afternoon naps, alcohol, tobacco, and caffeine before bedtime, sleeping alone, not using the bed for activities other than sleep, sleeping in a comfortable, quite, toxin-free environment, maintaining a stable sleep schedule, following a bedtime routine, and avoiding bedtime activities that are physiologically, cognitively, and emotionally activating. Studies on students have revealed that respecting sleep hygiene rules is correlated with higher sleep quality and lower sleepiness during the day [
45‐
49]. Nevertheless, some sleep hygiene domains seem to have a stronger impact on sleep quality and sleep duration than others [
50]. For instance, while avoiding electronic devices before sleep has been suggested to be a useful strategy [
51], little evidence exists that exercising in the evening has a negative impact on subsequent sleep [
52]. In summary, these findings suggest that the validity of sleep hygiene recommendations should be examined more thoroughly in future research [
50,
53]. Thus, having reliable and valid self-report measures is essential to gauge individual responses to behavioral interventions and evaluate sleep hygiene recommendations.
To assess sleep hygiene behavior, LeBourgeois et al. [
44] have developed the Adolescent Sleep Hygiene Scale (ASHS). The ASHS is a self-report questionnaire specifically designed to examine sleep hygiene in 12- to 19-year-old adolescents, referring to sleep hygiene practices during the past month. More recently, Storfer-Isser et al. [
54] have validated this instrument and developed a revised version (ASHSr), which contains six dimensions (physiological factor, behavior arousal factor, cognitive/emotional factor, daytime sleep factor, sleep environment factor, sleep stability factor), and which had improved psychometric properties, as described in more details in the methods section. The aim of the present study was to translate the English version into Farsi/Persian and to validate the Farsi/Persian version of the ASHSr. This endeavor is important because Iranian adolescents seem to share similar sleep pattern compared with adolescents for which the ASHSr was initially designed [
55]. To this end, a large sample of Iranian adolescents (see below) completed a series of questionnaires. We evaluated the factorial validity of the ASHSr using confirmatory factor analyses. Moreover, Cronbach’s alphas for the overall ASHSr index and the various ASHSr subscales were calculated to examine the internal consistency of the instrument. Test-retest reliability was assessed with a subsample of students. To assess the concurrent validity of the ASHSr, participants also completed the Pittsburg Sleep Quality Index (PSQI).
Discussion
The present study lends support to the 6-factor structure of the Farsi/Persian version of the ASHSr, confirms that all indices have satisfactory internal consistency, and shows that the ASHSr has adequate test-retest reliability. While significant correlations were found between the ASHSr and the PSQI (in support of concurrent validity of the instrument), the magnitude of the relationships was weak. Our findings add to the literature regarding the association between adolescents sleep hygiene practices and their sleep quality, which is still a relatively under-researched area. Developing instruments to assess sleep hygiene practices among Iranian adolescents is important because sleep complaints are highly prevalent in this target group. For instance, in the present sample, the percentage of students with low sleep quality was 63%, which is higher compared to previous studies with adolescents from New Zealand [
59] or Iran [
62], in which just over half of the participants were classified as poor sleepers.
The 6-factor structure found in the CFA is in line with a prior study with American adolescents [
54]. Compared to this study, three items had relatively low factor loadings. However, we decided to retain these items to ensure comparability with other studies, and because these items seemed clinically relevant. For instance, going to bed and think about things that need to be done and/or replaying the day’s events in one’s mind are representative of dysfunctional sleep-related cognitions, and therefore key elements of cognitive models of insomnia [
68,
69]. Not surprisingly, rumination and focusing proved to be associated with increased sleep complaints in previous investigations [
70]. Accordingly, these items might play an important role in sleep hygiene planning with adolescent samples. Since it is not fully clear why these items had low factor loadings, more research is needed to corroborate the results found in the present study.
Compared to the study of Storfer-Isser et al. [
54], the inspection of the single item descriptive statistics showed that Iranian adolescents reported considerable worse sleep hygiene practices than American youngsters, with Iranians having less favorable scores on 20 of 24 items. This is in line with a recent study in a nationwide sample of New Zealand adolescents reporting more favorable scores on the ASHS total index, and four subscales (physiological, cognitive/emotional, sleep environment, daytime sleep) [
59]. In the present sample of Iranian adolescents, the most frequently reported problematic sleep hygiene practices (exceeding the theoretical mean of 3.5) were (a) going to bed and thinking about things that need to be done, (b) going to bed an replaying the day’s events over and over in mind, (c) staying up longer and (d) “sleeping in” more than 1 h than usual bedtime/wake time during weekends, (e) drinking > 4 glasses of water/liquid 1 h before bedtime, and (f) drinking caffeine (e.g., cola pop, root bear, iced tea, coffee) after 6:00 pm. Thus, these issues seem to be the most important aspects of sleep hygiene that could be addressed in future intervention programmes.
Compared to American and New Zealand adolescents, better sleep practices were reported by Iranian adolescents with regard to the behavioral arousal factor, indicating that before bedtime, Iranian adolescents less frequently engage in activities that make them feel awake (e.g., playing video games, watching TV, talking on the telephone). Cultural differences with regard to sleep hygiene have been reported previously. For instance, LeBourgeois et al. [
44] found that Italian adolescents reported better sleep hygiene practices than American peers, which they explained by a stronger parental involvement into adolescence among Italian youngsters. To what extent parental involvement impacted on sleep hygiene practices among Iranian adolescents cannot be directly answered with the present data. However, at least two lines of research on sleep in Iranian children and adolescents suggest that parental involvement on adolescents’ sleep patterns is important: First, a sleep hygiene training for both parents and children with ADHD improved children’s sleep and psychological functioning [
36]. Second, from a former study [
35] on sleep and psychological functioning among 81 families in North-eastern Iran, it turned out that parents’ and children’s sleep patterns and psychological functioning were similar; importantly, this pattern of results was in line with previous research on sleep and psychological functioning in Swiss families [
34]. Given the obvious differences in sleep hygiene practices between adolescents from different cultures, clearly more knowledge is needed regarding the question of how psychological, social and environmental factors impact on sleep hygiene practices of adolescents in Western and non-Western societies.
With regard to the psychometric properties of the Farsi/Persian version of the ASHSr, we found higher Cronbach’s alpha values compared to previous research with American and Italian adolescents [
44,
54]. Moreover, despite the fact that the recall period of the ASHSr (past month) and the time interval between the first and the second measurement occasion (6 weeks) did not perfectly match in the present study, our findings show that the ASHSr indices have adequate test-retest reliability with strong correlations across a 6-week period.
With regard to concurrent validity, our findings are in line with previous studies using the ASHS/ASHSr showing that sleep hygiene indices are significantly associated with other subjective and objective sleep quality measures [
44,
54,
71‐
73] or in which worse sleep hygiene practices were reported by adolescents with insomnia compared to normal sleepers [
73]. Nevertheless, as in a previous study using actigraphy-based sleep outcomes (e.g. sleep duration, sleep efficiency, sleep onset latency) and self-reported daytime sleepiness [
54,
74], the strength of the relationships found between the ASHS instruments and other sleep indices was relatively weak (
r ≈ .20). The reasons for the low correlations are not fully understood, particularly as higher correlations were found between the ASHS and the PSQI among New Zealand adolescents [
59]. While the PSQI may not be an age-appropriate instrument to assess sleep quality in adolescents (e.g., the instrument does not measure the possible discrepancy between weekday and weekend sleep parameters) [
74], another explanation for the low correlations might be that sleep hygiene practices were relatively poor in the present sample, resulting in more limited variance compared to other samples. For instance, as reported in Table
1, only six ASHSr items were above the theoretical mean of
M = 3.5, whereas the remaining 18 items were below this threshold. Thus, there seems to be considerable scope for improvement with regard to sleep hygiene among Iranian adolescents. Hence, it would be interesting to see whether targeting healthy sleep hygiene practices among adolescents results in stronger correlations between the ASHSr and sleep outcomes in this specific target group [
49].
Some limitations need to be acknowledged that preclude an overgeneralization of the present findings: First, all data are based on self-reports. However, self-report questionnaires are still useful for large-sample research as time- and cost-effective tools. Second, testing the discriminative validity of the ASHSr was not possible because the findings are based on a non-clinical sample of adolescents. Third, convenience sampling was used to select participants. Therefore, the sample may not be fully representative of the entire Iranian student population. For instance, male students were slightly overrepresented in the present sample (57% boys vs. 43% girls). Moreover, a generalization to other age groups is not possible. Fourth, while we used the PSQI to assess concurrent validity, clinical interviews or other instruments such as the Insomnia Severity Index [
75,
76], which provide validated cut-off scores for subthreshold/moderate/severe insomnia, might have been more useful to relate the ASHSr with sleep complaints. Nevertheless, among adolescents, valid and reliable instruments to measure sleep hygiene practices are highly needed since adolescence is a period in which considerable changes in sleep/wake pattern, sleep duration, delay in the timing of sleep, and increasingly large discrepancies between weekday and weekend sleep pattern occur [
28,
44,
54]. Moreover, while many adolescents have limited awareness that sleep hygiene practices are closely associated with sleep quality [
49,
77‐
79], research suggests that sleep hygiene practices can be improved through adequate training [
46,
48,
80,
81]. Fourth, more evidence is needed with regard to the predictive validity of the ASHSr, which was not tested in the present study.