Development of evening sleep homeostatic pressure in early adolescent boys

The physiological processes governing sleep regulation show maturational changes during adolescent development. To date, data are available to specify when delays in circadian timing occur; however, no longitudinal data exist to characterize the maturation of the accumulation of sleep pressure across the evening. The aim of this longitudinal study was to test whether this change in evening sleep propensity can be identified during early adolescence. Twenty pre-pubescent boys' (Mage = 10.3, SD = 0.4 years) evening sleep homeostats were assessed using a series of sleep latency tests every hour (7:30 p.m. to 3:30 a.m.) at 6-month intervals across four waves. While results revealed shorter sleep onset latencies with increasing wakefulness (p < .001), this effect was not moderated by study wave (p = .79). Evening sleep propensity thus appears to remain stable in boys during early adolescence. Future studies should expand upon these findings by using larger samples of girls as well as boys across an extended age range during the teenage years.

Low-intensity scheduled morning exercise for adolescents with a late chronotype: a novel treatment to advance circadian phase?

Study Objectives

During adolescence, an interplay between biological and environmental factors leads to constrained sleep duration and timing. The high prevalence of sleep deprivation during this developmental period is a public health concern, given the value of restorative sleep for mental, emotional, and physical health. One of the primary contributing factors is the normative delay of the circadian rhythm. Therefore, the present study aimed to evaluate the effect of a gradually advanced morning exercise schedule (30 min shift each day) completed for 45 min on 5 consecutive mornings, on the circadian phase and daytime functioning of adolescents with a late chronotype, compared with a sedentary control group.

Methods

A total of 18 physically inactive male adolescents aged 15-18 years spent 6 nights at the sleep laboratory. The morning procedure included either 45 min walking on a treadmill or sedentary activities in dim light. Saliva dim light melatonin onset, evening sleepiness, and daytime functioning were assessed during the first and last night of laboratory attendance.

Results

The morning exercise group had a significantly advanced (earlier) circadian phase (27.5 min ± 32.0), while sedentary activity resulted in a phase delay (-34.3 min ± 53.2). Morning exercise also led to higher evening sleepiness in the earlier hours of the night, but not at bedtime. Mood measures improved slightly in both study conditions.

Conclusions

These findings highlight the phase-advancing effect of low-intensity morning exercise among this population. Future studies are needed to test the transference of these laboratory findings to adolescents' real life.

Sleep duration and mood in adolescents: an experimental study

STUDY OBJECTIVES

This study examines the relationship between experimentally manipulated sleep duration and mood in adolescents.

METHODS

Thirty-four adolescents (20 male), aged 15-17 years, lived in a sleep laboratory for 10 days and 9 nights. They were allocated to one of three sleep "doses" for five consecutive nights for 5, 7.5, or 10 h sleep opportunity per night. Two baseline nights and two recovery nights entailed 10 h sleep opportunity per night. Mood was measured every 3 h during wake using unipolar visual analogue scales measuring the mood states "depressed," "afraid," "angry," "confused," "anxious," "happy," and "energetic."

RESULTS

Mixed models analyses with post hoc comparisons revealed that participants in the 5-h group, but not the 7.5- or 10-h groups, reported being significantly more depressed, angry, and confused during sleep restriction than at baseline. Adolescents were significantly less happy and energetic during sleep restricted to 5 h and significantly less energetic during sleep restricted to 7.5 h. When adolescents had 10 h sleep opportunities their happiness significantly increased. No statistically significant effects of sleep restriction were found for fear or anxiety, although small-to-moderate effects of sleep restricted to 5 or 7.5 h were found. Two nights of recovery sleep was not sufficient to recover from increased negative mood states for the 5-h group, although recovery occurred for positive mood states.

CONCLUSIONS

Given the prevalence of insufficient sleep and the rising incidence of mood disorders and dysregulation in adolescents, these findings highlight the importance of sufficient sleep to mitigate these risks.

Homeostatic Response to Sleep Restriction in Adolescents

The high prevalence of chronic sleep restriction in adolescents underscores the importance of understanding how adolescent sleep is regulated under such conditions. One component of sleep regulation is a homeostatic process: if sleep is restricted, then sleep intensity increases. Our knowledge of this process is primarily informed by total sleep deprivation studies and has been incorporated in mathematical models of human sleep regulation. Several animal studies, however, suggest that adaptation occurs in chronic sleep restriction conditions, showing an attenuated or even decreased homeostatic response. We investigated the homeostatic response of adolescents to different sleep opportunities. Thirty-four participants were allocated to one of three groups with 5, 7.5 or 10 h of sleep opportunity per night for 5 nights. Each group underwent a protocol of 9 nights designed to mimic a school week between 2 weekends: 2 baseline nights (10 h sleep opportunity), 5 condition nights (5, 7.5 or 10 h), and two recovery nights (10 h). Measures of sleep homeostasis (slow-wave activity and slow-wave energy) were calculated from frontal and central EEG derivations and compared to predictions derived from simulations of the homeostatic process of the two-process model of sleep regulation. Only minor differences were found between empirical data and model predictions, indicating that sleep homeostasis is preserved under chronic sleep restriction in adolescents. These findings improve our understanding of effects of repetitive short sleep in adolescents.

The roles of repetitive negative thinking and perfectionism in explaining the relationship between sleep onset difficulties and depressed mood in adolescents

OBJECTIVE

The present study investigated the relationship between difficulty initiating sleep and depressed mood and whether it is mediated by repetitive negative thinking. A moderating role of perfectionism was also examined.

METHODS

We surveyed 393 adolescents aged 14 to 20 years (M = 17.32, SD = 1.90) via an online questionnaire that assessed difficulty initiating sleep, repetitive negative thinking, perfectionism, and depressed mood.

RESULTS

Results indicated that repetitive negative thinking fully mediated the relationship between difficulty initiating sleep and depressed mood. In addition, this relationship was moderated by perfectionism, specifically, the relationship between repetitive negative thinking and depressed mood was stronger among more perfectionistic adolescents.

CONCLUSIONS

These findings highlight that repetitive negative thinking is significantly associated with both difficulty initiating sleep and depressed mood, supporting the conceptualization of repetitive negative thinking as a transdiagnostic process. Further, individual differences in perfectionism may amplify the relationship between repetitive negative thinking and mood. The role of repetitive negative thinking and perfectionism in explaining the link between sleep onset problems and depressed mood has important clinical implications through providing possible treatment targets.

How internal and external cues for bedtime affect sleep and adaptive functioning in adolescents

OBJECTIVE

To determine whether the main reason for bedtime is associated with sleep and adaptive functioning in adolescents.

METHODS

Participants were 1374 adolescents (X age = 16.8 years, SD = 0.58; 33.6% male) from Helsinki, Finland. Adolescents completed a questionnaire battery including the Munich Chronotype Questionnaire, Strengths and Difficulties Questionnaire, Beck Depression Inventory, and items drawn from the School Sleep Habits Survey, and the Pittsburgh Sleep Quality Index.

RESULTS

On school nights, adolescents whose parents set their bedtime, and those who went to bed when they were tired went to bed earlier, obtained more sleep and had earlier midpoint of sleep than adolescents who went to bed when they have finished messaging/socializing or when their television show had finished. Adolescents who went to bed when they had finished their homework had sleep that fell in between these groups. On weekends, adolescents whose parents set their bedtime went to bed earlier and had an earlier midpoint of sleep. However, there were no differences between groups in terms of sleep duration once the need to rise for school in the morning was removed. Adolescents who went to bed on school nights when they were tired or once their homework was finished had better adaptive functioning.

CONCLUSIONS

These results provide support for two very different approaches to help optimize the sleep of adolescents: either by implementing parental regulation of bedtimes across adolescence, or by encouraging adolescents to use their bodily cues to indicate when it is time for bed, rather than relying on an external cue.

Variability of the cortisol awakening response and morning salivary oxytocin in late adolescence

Exogenously administered oxytocin interacts with the hypothalamic-pituitary-adrenal (HPA) axis to modulate endogenous cortisol levels, suggesting a synergistic role for these two hormones in the response to stress, cognitive performance and the development of psycho-behavioural disorders. The cortisol awakening response (CAR) is considered a reliable measure of HPA axis function in humans. However, the CAR appears to vary considerably from day to day and may be strongly influenced by the anticipated demands of the day ahead. The level of variation intrinsic to the CAR is unclear because few studies have examined the CAR in the absence of daily environmental variation. It is not known whether oxytocin has a similar or complementary awakening response. Therefore, over three consecutive days, we examined 12 adolescents (aged 15-17 years) in a highly-controlled sleep laboratory. Saliva was collected on days 4-6 of a 9-day laboratory visit. Cortisol and oxytocin levels were determined by an enzyme-linked immunosorbent assay from saliva sampled at 0, 15, 30 and 45 minutes, and 8 and 12 hours post-awakening. CAR magnitude varied between days and was associated with sleep duration and pre-awakening sleep stage. Conversely, oxytocin levels dropped dramatically in the first 15 minutes post-awakening and were highly consistent across participants and days. Older participants had higher awakening oxytocin concentrations. Although cortisol increases and oxytocin rapidly declines upon awakening, their diurnal variation does not appear to be related at basal, peripheral levels, consistent with a previous finding that exogenously administered oxytocin only modulates cortisol under conditions of stress.

Sleep duration and risk-taking in adolescents: A systematic review and meta-analysis

Risk-taking is associated with increased morbidity and mortality among adolescents, with insufficient sleep a potential factor contributing to heightened risk-taking propensity in this age group. A systematic review of the evidence examining the relationship between sleep duration and risk-taking in adolescents was conducted using PsycINFO, PubMed, Medline, Scopus, and CINAHL databases. These searches identified 26 studies including 579,380 participants, 24 of which were appropriate for meta-analysis. Pooled results indicated that insufficient sleep was associated with 1.43 [1.26, 1.62] times greater odds of risk-taking. This relationship was witnessed across diverse categories of risk-taking, including alcohol use, drug use, smoking, violent/delinquent behaviour, transport risk-taking/road safety, sexual risk-taking and trait risk-taking. Risk of bias analysis showed that the quality of the included studies was mixed. Further, few studies utilized either longitudinal or experimental designs, thus limiting causal conclusions. These findings highlight the importance of further research to examine the causal relationship between sleep duration and risk-taking and to elucidate the mechanisms that underpin this relationship.

Sleep spindles in adolescence: a comparison across sleep restriction and sleep extension

BACKGROUND

The tendency for adolescents to have restricted sleep has been examined in numerous studies; however, the impact of sleep restriction on adolescents' neural activity during sleep (measured by electroencephalography (EEG)) is less extensively researched, particularly regarding sleep spindles.

METHODS

In this experimental study, 34 adolescents attended a 10-day laboratory study where they received five consecutive nights of either 5 h, 7.5 h or 10 h of sleep opportunity, with one adaptation, one baseline and two recovery nights of 10 h of sleep opportunity before and after the experimental phase.

RESULTS

Both within- and between-subjects effects were observed for fast sleep spindle characteristics of density, duration and amplitude. Overall, when experiencing severe sleep restriction, fast spindles in adolescents were lower in amplitude and longer in duration. Sex differences were also seen for fast spindle amplitude.

CONCLUSIONS

This investigation adds to the knowledge in this field by investigating specific sleep spindle characteristics in the context of experimentally manipulated sleep. Sleep restriction is highly prevalent among adolescents. These findings indicate that chronic sleep restriction has an impact on brain activity related to sleep spindles.

Reliability of sleep spindle measurements in adolescents: How many nights are necessary?

Evidence of night-to-night variation in adolescent sleep spindle characteristics is lacking. Twelve adolescents (M = 15.8 ± 0.8 years, eight males) participated in a laboratory study involving 9 nights with 10 hr sleep opportunity. Sleep electroencephalograph was analysed and intra-class coefficients calculated to determine the reliability of sleep spindles across multiple nights of recording. Slow spindle amplitude and fast spindle density, duration and amplitude characteristics all had acceptable reliability within a single night of sleep recording. Slow spindle density and duration measurements needed a minimum of 4 and 2 nights, respectively, for reliable estimation. Theoretical and methodological implications are discussed.

Sleep Loss and Affective Functioning: More Than Just Mood

Empirical evidence supports an intimate link between sleep and affective functioning. While the bidirectional relationship between sleep duration and mood is well documented, limited research targets other aspects of affective functioning, such as emotion and emotion regulation, or considers their interrelationships. The present review summarizes research examining the relationship between sleep and emotion, emotion regulation, and mood, and presents a theoretical model representing the relationships between these constructs. Disruptions to sleep and mood may trigger and maintain a negative cascade, leading to more entrenched sleep problems and psychopathology. Given that insufficient sleep is a widespread phenomenon, understanding the interrelationships between sleep and affective functioning has implications for both public health and clinical practice.

How Many Sleep Diary Entries Are Needed to Reliably Estimate Adolescent Sleep?

Study Objectives

To investigate (1) how many nights of sleep diary entries are required for reliable estimates of five sleep-related outcomes (bedtime, wake time, sleep onset latency [SOL], sleep duration, and wake after sleep onset [WASO]) and (2) the test-retest reliability of sleep diary estimates of school night sleep across 12 weeks.

Methods

Data were drawn from four adolescent samples (Australia [n = 385], Qatar [n = 245], United Kingdom [n = 770], and United States [n = 366]), who provided 1766 eligible sleep diary weeks for reliability analyses. We performed reliability analyses for each cohort using complete data (7 days), one to five school nights, and one to two weekend nights. We also performed test-retest reliability analyses on 12-week sleep diary data available from a subgroup of 55 US adolescents.

Results

Intraclass correlation coefficients for bedtime, SOL, and sleep duration indicated good-to-excellent reliability from five weekday nights of sleep diary entries across all adolescent cohorts. Four school nights was sufficient for wake times in the Australian and UK samples, but not the US or Qatari samples. Only Australian adolescents showed good reliability for two weekend nights of bedtime reports; estimates of SOL were adequate for UK adolescents based on two weekend nights. WASO was not reliably estimated using 1 week of sleep diaries. We observed excellent test-rest reliability across 12 weeks of sleep diary data in a subsample of US adolescents.

Conclusion

We recommend at least five weekday nights of sleep dairy entries to be made when studying adolescent bedtimes, SOL, and sleep duration. Adolescent sleep patterns were stable across 12 consecutive school weeks.

Continental-scale variation in chloride/bromide ratios of wet deposition

Chlorine and bromine play crucial roles in atmospheric element cycles and are important environmental tracers in catchment investigations, so understanding their distribution at the Earth's near-surface is imperative for deciphering their behaviour. This study presents the first continental-scale analysis of Cl^- and Br^- concentrations of wet deposition, based on six and half years of weekly samples collected across North America. A recently developed imputation algorithm was applied to estimate the high proportion of censored Br^- values, as well as the other eight analytes, based on the multivariate relationships of nine analytes. The results are consistent with previous studies that have found that the concentrations of these two ions in wet deposition, and the Cl^-/Br^- ratios of wet deposition decrease with distance inland. Close to the coast, Cl^-/Br^- ratios of wet deposition are similar to the ratio found in seawater (~288 by mass), rapidly decrease to approximately a third of the seawater ratio at ~200km inland, and then decrease at a much lesser rate to reach mass-ratios of 20 to 10 at ~1500km inland, following a logarithmic regression. The Niagara Falls and the Great Salt Lake are identified as localised sources of atmospheric solutes based on elevated Cl^-/Br^- ratios of wet deposition at proximal sites. Our observations provide further confidence in the findings presented in previous studies that have shown that Cl^-/Br^- ratios systematically decrease with increasing distance from the coast, despite the potential confounding impact of other processes, such as weather patterns, chemical behaviour and anthropogenic activity. Our results provide improved estimates of Cl^-/Br^- ratios of wet deposition source water in the absence of site-specific data.

An investigation of the longitudinal relationship between sleep and depressed mood in developing teens

OBJECTIVE

The prospective, bidirectional relationship between sleep disturbance and depressed mood was assessed in a school-based sample of adolescents.

METHOD

One hundred and thirty-eight Australian adolescents (mean age time 1 =15.69, standard deviation =0.92; 64% male) completed questionnaires to assess sleep parameters and depressed mood, on two occasions over 1 year.

RESULTS

Cross-sectional associations were observed between depressed mood and sleep duration, as well as wakefulness in bed. Prospective analyses revealed depressed mood predicted less total sleep time on school nights and a longer latency to sleep onset on weekends 1 year later. There was no prospective support for sleep predicting later depressed mood.

CONCLUSION

Contrary to prediction, our results suggest in this case that depressed mood may act as a precursor to poor sleep rather than the converse.

The effect of split sleep schedules (6h-on/6h-off) on neurobehavioural performance, sleep and sleepiness

Shorter, more frequent rosters, such as 6h-on/6h-off split shifts, may offer promise to sleep, subjective sleepiness and performance by limiting shift length and by offering opportunities for all workers to obtain some sleep across the biological night. However, there exists a paucity of studies that have examined these shifts using objective measures of sleep and performance. The present study examined neurobehavioural performance, sleepiness and sleep during 6h-on/6h-off split sleep schedules. Sixteen healthy adults (6 males, 26.13 y ± 4.46) participated in a 9-day laboratory study that included two baseline nights (BL, 10h time in bed (TIB), 2200 h-0800 h), 4 days on one of two types of 6h-on/6h-off split sleep schedules with 5h TIB during each 'off' period (6h early: TIB 0300 h-0800 h and 1500 h-20000 h, or 6-h late: TIB 0900 h-1400 h and 2100 h-0200 h), and two recovery nights (10h TIB per night, 2200 h-0800 h). Participants received 10h TIB per 24h in total across both shift schedules. A neurobehavioural test bout was completed every 2 h during wake, which included the Psychomotor Vigilance Task (PVT) and the Karolinska Sleepiness Scale (KSS). Linear mixed effects models were used to assess the effect of day (BL, shift days 1-4), schedule (6h early, 6h late) and trial (numbers 1-6) on PVT lapses (operationalised as the number of reaction times >500 ms), PVT total lapse time, PVT fastest 10% of reaction times and KSS. Analyses were also conducted examining the effect of day and schedule on sleep variables. Overall, PVT lapses and total lapse time did not differ significantly between baseline and shift days, however, peak response speeds were significantly slower on the first shift day when compared to baseline, but only for those in the 6h-late condition. Circadian variations were apparent in performance outcomes, with individuals in the 6h-late condition demonstrated significantly more and longer lapses and slower peak reaction times at the end of their night shift (0730 h) than at any other time during their shifts. In the 6h-early condition, only response speed significantly differed across trials, with slower response speeds occurring at trial 1 (0930 h) than in trials 3 (1330 h) or 4 (2130 h). While subjective sleepiness was higher on shift days than at baseline, sleepiness did not accumulate across days. Total sleep was reduced across split sleep schedules compared to baseline. Overall, these results show that while there was not a cumulative cost to performance across days of splitting sleep, participants obtained less sleep and reported lowered alertness on shift days. Tests near the circadian nadir showed higher sleepiness and increased performance deficits. While this schedule did not produce cumulative impairment, the performance deficits witnessed during the biological night are still of operational concern for industry and workers alike.

A systematic review of the sleep, sleepiness, and performance implications of limited wake shift work schedules

OBJECTIVES

The aim of this review was to identify which limited wake shift work schedules (LWSW) best promote sleep, alertness, and performance. LWSW are fixed work/rest cycles where the time-at-work does is ≤8 hours and there is >1 rest period per day, on average, for ≥2 consecutive days. These schedules are commonly used in safety-critical industries such as transport and maritime industries.

METHODS

Literature was sourced using PubMed, Embase, PsycInfo, Scopus, and Google Scholar databases. We identified 20 independent studies (plus a further 2 overlapping studies), including 5 laboratory and 17 field-based studies focused on maritime watch keepers, ship bridge officers, and long-haul train drivers. The measurement of outcome measures was varied, incorporating subjective and objective measures of sleep: sleep diaries (N=5), actigraphy (N=4), and polysomnography, (N=3); sleepiness: Karolinska Sleepiness Scale (N=5), visual analog scale (VAS) alertness (N=2) and author-derived measures (N=2); and performance: Psychomotor Vigilance Test (PVT) (N=5), Reaction Time or Vigilance tasks (N=4), Vector and Letter Cancellation Test (N=1), and subjective performance (N=2).

RESULTS

Of the three primary rosters examined (6 hours-on/6 hours-off, 8 hours-on/8 hours-off and 4 hours-on/8 hours-off), the 4 hours-on/8 hours-off roster was associated with better sleep and lower levels of sleepiness. Individuals working 4 hours-on/8 hours-off rosters averaged 1 hour more sleep per night than those working 6 hours-on/6 hours-off and 1.3 hours more sleep than those working 8 hours-on/8 hours-off (P<0.01). More broadly, findings indicate that LWSW schedules were associated with better sleep and lower sleepines in the case of (i) shorter time-at-work, (ii) more frequent rest breaks, (iii) shifts that start and end at the same clock time every 24 hours, and (iv) work shifts commencing in the daytime (as opposed to night). The findings for performance remain incomplete due to the small number of studies containing a performance measure and the heterogeneity of performance measures within those that did.

CONCLUSION

The literature supports the utility of LWSW in industries where individuals sleep at or near the workplace as they facilitate at least some sleep during the biological night and minimize deficits associated with time-on-shift with shorter shifts. Overall, the 4 hour-on/8 hour-off roster best promoted sleep and minimized sleepiness compared to other LWSW schedules. Nevertheless, and considering the safety-critical nature of industries which employ LWSW, the limited literature needs to be greatly expanded with specific focus on the consequences for performance and comparison to mainstream rosters.

Adolescents who perceive fewer consequences of risk-taking choose to switch off games later at night

AIM

Technology use by adolescents close to bedtime commonly leads to sleep problems, and individual factors predicting those at heightened risk are under studied. We investigated whether risk-taking perceptions influenced length of adolescent technology use at bedtime and whether being aware of time moderated this association.

METHODS

We recruited 16 males and five females, with a mean age of 17.6 years, from school and university populations to assess adolescent technology use and bedtimes. They were assessed for trait risk-taking using the Cognitive Appraisal of Risky Events questionnaire and had unrestrained access to a video game on two separate nights, counterbalanced for clock present or clock absent conditions. The adolescents' self-selected bedtime provided a measure of the level of technology use and was the dependent variable.

RESULTS

Adolescents who perceived fewer negative consequences of risky activities on the Cognitive Appraisal of Risky Events played the video game longer and went to bed later than those who perceived more negative consequences (p = 0.03). There was no influence on bedtimes from perceived benefits of risk-taking or clock presence.

CONCLUSION

Adolescents who perceived fewer negative consequences of risk-taking were more likely to stay up later using technology, facing a heightened risk of displaced sleep.

The effect of one night's sleep deprivation on adolescent neurobehavioral performance

STUDY OBJECTIVES

To investigate the effects of one night's sleep deprivation on neurobehavioral functioning in adolescents.

DESIGN

Participants completed a neurobehavioral test battery measuring sustained attention, reaction speed, cognitive processing speed, sleepiness, and fatigue every 2 h during wakefulness. Baseline performance (defined as those test bouts between 09:00 and 19:00 on days 2 and 3, following two 10-h sleep opportunities) were compared to performance at the same clock time the day following total sleep deprivation.

SETTING

The sleep laboratory at the Centre for Sleep Research.

PARTICIPANTS

Twelve healthy adolescents (6 male), aged 14-18 years (mean = 16.17, standard deviation = 0.83).

MEASUREMENTS AND RESULTS

Sustained attention, reaction speed, cognitive processing speed, and subjective sleepiness were all significantly worse following one night without sleep than following 10-h sleep opportunities (all main effects of day, P < 0.05). Sleep deprivation led to increased variability on objective performance measures. There were between-subjects differences in response to sleep loss that were task-specific, suggesting that adolescents may not only vary in terms of the degree to which they are affected by sleep loss but also the domains in which they are affected.

CONCLUSIONS

These findings suggest that one night of total sleep deprivation has significant deleterious effects upon neurobehavioral performance and subjective sleepiness. These factors impair daytime functioning in adolescents, leaving them at greater risk of poor academic and social functioning and accidents and injuries.

Identifying adolescent sleep problems

OBJECTIVES

To examine the efficacy of self-report and parental report of adolescent sleep problems and compare these findings to the incidence of adolescents who fulfill clinical criteria for a sleep problem. Sleep and daytime functioning factors that predict adolescents' self-identification of a sleep problem will also be examined.

METHOD

308 adolescents (aged 13-17 years) from eight socioeconomically diverse South Australian high schools participated in this study. Participants completed a survey battery during class time, followed by a 7-day Sleep Diary and the Flinders Fatigue Scale completed on the final day of the study. Parents completed a Sleep, Medical, Education and Family History Survey.

RESULTS

The percentage of adolescents fulfilling one or more of the criteria for a sleep problem was inordinately high at 66%. Adolescent self-reporting a sleep problem was significantly lower than the adolescents who had one or more of the clinical criteria for a sleep problem (23.1% vs. 66.6%; χ(2) = 17.46, p<.001). Parental report of their adolescent having a sleep problem was significantly lower than adolescent self-report (14.3% vs. 21.1%, p<.001). Adolescents who reported unrefreshing sleep were 4.81 times more likely to report a sleep problem. For every hour that bedtime was delayed, the odds of self-reporting a sleep problem increased by 1.91 times, while each additional 10 minutes taken to fall asleep increased the odds 1.40 times.

CONCLUSION

While many adolescents were found to have sleep patterns indicative of a sleep problem, only a third of this number self-identify having a sleep problem, while only a sixth of this number are indicated by parental report. This study highlights important features to target in future sleep education and intervention strategies for both adolescents and parents.

Estimating adolescent sleep patterns: parent reports versus adolescent self-report surveys, sleep diaries, and actigraphy

BACKGROUND

In research and clinical contexts, parent reports are often used to gain information about the sleep patterns of their adolescents; however, the degree of concordance between parent reports and adolescent-derived measures is unclear. The present study compares parent estimates of adolescent sleep patterns with adolescent self-reports from surveys and sleep diaries, together with actigraphy.

METHODS

A total of 308 adolescents (59% male) aged 13-17 years completed a school sleep habits survey during class time at school, followed by a 7-day sleep diary and wrist actigraphy. Parents completed the Sleep, Medical, Education and Family History Survey.

RESULTS

Parents reported an idealized version of their adolescent's sleep, estimating significantly earlier bedtimes on both school nights and weekends, significantly later wake times on weekends, and significantly more sleep than either the adolescent self-reported survey, sleep diary, or actigraphic estimates.

CONCLUSION

Parent reports indicate that the adolescent averages a near-optimal amount of sleep on school nights and a more than optimal amount of sleep on weekends. However, adolescent-derived averages indicate patterns of greater sleep restriction. These results illustrate the importance of using adolescent-derived estimates of sleep patterns in this age group and the importance of sleep education for both adolescents and their parents.

The sleep patterns and well-being of Australian adolescents

AIM

Adolescent sleep patterns vary between countries, and these differences influence adolescent functioning and well-being. The present study provides data on the sleep and well-being of Australian adolescents.

METHODS

385 adolescents aged 13-18 years were recruited from 8 South Australian schools spanning the socio-economic spectrum. Adolescents completed survey battery during class time at school, followed by a 7-day sleep diary.

RESULTS

Australian adolescents, on average, obtained inadequate sleep across the school week. Adolescents commonly reported difficulty initiating sleep, unrefreshing sleep, and the subjective feeling of restless legs. Problematic levels of sleepiness, fatigue, depressed mood and anxiety were highly prevalent. Later bedtimes, longer sleep onset latencies, and shorter sleep duration were significantly associated with aspects of poor daytime functioning.

CONCLUSION

These results add to our knowledge of adolescent sleep and well-being worldwide. They also highlight the need for greater attention to sleep during this phase of development, when future behaviors and outcomes are being shaped.

A cross-cultural comparison of sleep duration between US And Australian adolescents: the effect of school start time, parent-set bedtimes, and extracurricular load

STUDY OBJECTIVE

To test whether sleep duration on school nights differs between adolescents in Australia and the United States and, if so, whether this difference is explained by cultural differences in school start time, parental involvement in setting bedtimes, and extracurricular commitments.

PARTICIPANTS

Three hundred eighty-five adolescents aged 13 to 18 years (M = 15.57, SD = 0.95; 60% male) from Australia and 302 adolescents aged 13 to 19 years (M = 16.03, SD = 1.19; 35% male) from the United States.

METHODS

Adolescents completed the School Sleep Habits Survey during class time, followed by an 8-day sleep diary.

RESULTS

After controlling for age and gender, Australian adolescents obtained an average of 47 minutes more sleep per school night than those in the United States. Australian adolescents were more likely to have a parent-set bedtime (17.5% vs. 6.8%), have a later school start time (8:32 a.m. vs. 7:45 a.m.), and spend less time per day on extracurricular commitments (1 h 37 min vs. 2 h 41 min) than their U.S. peers. The mediating factors of parent-set bedtimes, later school start times, and less time spent on extracurricular activities were significantly associated with more total sleep.

CONCLUSIONS

In addition to biological factors, extrinsic cultural factors significantly affect adolescent sleep. The present study highlights the importance of a cross-cultural, ecological approach and the impact of early school start times, lack of parental limit setting around bedtimes, and extracurricular load in limiting adolescent sleep.

Insomnia and its symptoms in adolescents: comparing DSM-IV and ICSD-II diagnostic criteria

STUDY OBJECTIVES

Many studies of adolescent insomnia use experience of insomnia-like symptoms to categorize "caseness." This is likely to lead to inflated prevalence and may have important ramifications for the research using individual symptoms to operationalize insomnia. The aim of the present study was to contrast the occurrence of insomnia symptoms with cases of insomnia diagnosed using criteria from the fourth edition of the Diagnostic and Statistical Manual for Mental Disorders (DSM-IV) and the second edition of the International Classification of Sleep Disorders (ICSD-II) in a sample of Australian adolescents.

METHODS

Data were collected from 384 representative Australian adolescents aged 13-18 years old (59% male). During school hours, adolescents completed a comprehensive questionnaire battery targeting insomnia criteria and then completed a sleep diary for 7 days.

RESULTS

Insomnia symptoms were frequently reported by adolescents (e.g., 34.6% for frequent sleep-related daytime consequences). The proportion of adolescents meeting the diagnositc criteria for insomnia was much smaller: 10.9% of adolescents were classified as having General Insomnia using ICSD-II criteria, and 7.8% were classified as having Primary Insomnia according to DSM-IV criteria. ICSD-II Psychophysiological Insomnia was observed in 3.4% of adolescents. Insomnia diagnoses did not vary according to age, gender, school grade, or socioeconomic status. Using the ICSD-II criteria for General Insomnia resulted in a significantly higher number of insomnia diagnoses than did DSM-IV criteria for Primary Insomnia (p < 0.001) and ICSD-II Psychophysiological Insomnia (p < 0.001).

CONCLUSIONS

These results reveal that approximately 3 adolescents in the average classroom of 30 are likely to meet the diagnostic criteria for insomnia, while many more will have insomnia symptoms. There were significant differences in prevalence rates, depending on how insomnia was operationalized.

Time for bed: parent-set bedtimes associated with improved sleep and daytime functioning in adolescents

STUDY OBJECTIVES

To determine the proportion of adolescents whose bedtime is set by their parents and to evaluate whether parent-set bedtimes are associated with earlier bedtimes, more sleep, and better daytime functioning.

PARTICIPANTS

385 adolescents aged 13-18 years (mean = 15.6, SD = 0.95; 60% male) from 8 socioeconomically diverse schools in South Australia.

MEASUREMENTS AND METHODS

Adolescents completed the School Sleep Habits Survey during class time and then completed an 8-day Sleep Diary. The Flinders Fatigue Scale was completed on the final day of the study.

RESULTS

17.5% of adolescents reported a parent-set bedtime as the main factor determining their bedtime on school nights. Compared to adolescents without parent-set bedtimes, those with parent-set bedtimes had earlier bedtimes, obtained more sleep, and experienced improved daytime wakefulness and less fatigue. They did not differ significantly in terms of time taken to fall asleep. When parent-set bedtimes were removed on weekends, sleep patterns did not significantly differ between groups.

CONCLUSIONS

Significant personal and public health issues, such as depression and accidental injury and mortality, are associated with insufficient sleep. Converging biological and psychosocial factors mean that adolescence is a period of heightened risk. Parent-set bedtimes offer promise as a simple and easily translatable means for parents to improve the sleep and daytime functioning of their teens.

Polarization effects in the excitation and emission of Fe(3+) in orthoclase and their relevance to the determination of lattice sites of unknown defects

A method was recently proposed for determining possible lattice sites of an unknown defect from polarization effects in its optical transitions. In this paper the method is tested using the optically excited 1.77 eV (700 nm) fluorescence of Fe(3+) ions which predominantly occupy the T1 sites in orthoclase feldspar. The emission intensity depended on the polarization of the exciting photons and the emission was itself polarized. Two pairs of crystal field symmetry directions were deduced from polarization data for each of the transitions at 1.77, 2.79 and 3.26 eV, and one pair was aligned with symmetry axes in the average geometry of the four anions around the T1 sites. An analysis of EPR data for Fe(3+) ions in feldspar showed that there was a symmetry axis in the crystal field similar to one of those deduced from the polarization data. Group theory calculations were used to determine if the transitions were dipolar-a major assumption of the method. Three symmetries (S(4), C(2v) and C(2)) were found to lead to dipolar transitions consistent with the excitation results, and four (D(2), C(3), C(2) and C(s)) were consistent with a 1.77 eV dipolar emission.

Improved antimicrobial interventions have benefits

Studies have shown benefits to patients from improved interventions involving antimicrobial therapy. The purpose of the present study was to evaluate prospectively the impact of improved interventions by (i) the use of TheraTrac 2, a computer software program which electronically links susceptibility testing results immediately to the pharmacy and alerts pharmacists of potential interventions, and (ii) the education of pharmacists involving microbiologic topics. The study group had the new intervention program. The control group had interventions performed the way that they had previously been done by manually reviewing hard copies of susceptibility testing data. In a 5-month period, all inpatients whose last names began with A to K were the study group; inpatients whose last names began with L to Z were controls. Three analyses were done; one analysis (analysis A) involved only patients with interventions, one analysis (analysis B) involved all patients for whom antimicrobial testing was done and who were matched for diagnosis-related groups (DRGs), regardless of whether an intervention occurred, and one analysis (analysis C) involved these DRG-matched patients by using severity-adjusted data. In analysis A, the study group had a 4.8% decreased rate of mortality, an average of a 16.5-day decreased length of stay per patient, and $20,886 decreased variable direct costs per patient. None of these differences was statistically significant. In analysis B, the study patients had a 1.2% higher mortality rate (P = 0.741), an average of a 2.7-day decreased length of stay per patient (P = 0.035), and $2,626 decreased variable direct costs per patient (P = 0.008). In analysis C, the study patients had a 1.4% lower mortality rate, a 1.2-day decreased length of stay per patient, and $1,466 decreased variable direct costs per patient. In conclusion, the institution of this program caused substantial cost savings.

The PNH phenotype cells that emerge in most patients after CAMPATH-1H therapy are present prior to treatment

Paroxysmal nocturnal haemoglobinuria (PNH) cells are deficient in glycosylphosphatidylinositol (GPI) linked antigens due to a somatic mutation of the PIG-A gene in a haemopoietic stem cell. It appears that a PNH clone reaches detectable proportions only when there is selection in its favour. GPI-deficient T lymphocytes have been identified in patients treated with CAMPATH-1H, a monoclonal antibody against the GPI-linked CD52 molecule. CAMPATH-1H selects for cells that are deficient in CD52 (such as PNH-like cells) promoting the development of a PNH-like clone (analogous to PNH). We report that 10/15 patients with chronic lymphocytic leukaemia developed PNH-like lymphocytes after therapy with CAMPATH-1H. The remaining five patients developed no PNH-like cells at any stage, including one patient who received 12 weeks of therapy. The inactivating PIG-A mutation has been identified in one patient. This mutation was detectable by an extremely sensitive mutation-specific PCR-based analysis in the patient's mononuclear cells prior to CAMPATH-1H therapy. The frequency and phenotype of GPI-deficient lymphocytes after CAMPATH-1H and the detection of a PIG-A mutation in the lymphocytes prior to CAMPATH-1H therapy indicated that such mutations were present in a very small proportion of cells prior to selection in their favour by CAMPATH-1H. This suggests that a large proportion of individuals have cells with PIG-A mutations that are not detectable by flow cytometry and thus may have the potential to develop PNH.

Residual disease detection using fluorescent polymerase chain reaction at 20 weeks of therapy predicts clinical outcome in childhood acute lymphoblastic leukemia

PURPOSE

Ninety-five percent of children with acute lymphoblastic leukemia (ALL) will achieve a remission, but approximately 25% will relapse. Identifying these patients is difficult, as patients with adverse prognostic features at presentation are rare and the majority are standard risk. Analysis of minimal residual disease (MRD) may be able to determine those at risk of relapse, but the best method by which this can be accomplished has yet to be defined. The object of this study was to determine the predictive value of residual disease detection in a group of standard-risk patients with precursor-B ALL at a fixed point in therapy (week 20) using a simple fluorescent consensus immunoglobulin H (IgH) heavy chain polymerase chain reaction (PCR).

PATIENTS AND METHODS

Forty-two patients who presented with precursor-B ALL with standard-risk clinical features and treated according to either the Medical Research Council (MRC) UKALL X or XI protocols were assessed using a combination of both fluorescent consensus framework I and framework III Ig heavy-chain PCR. The results of the PCR were analyzed on an ABI 373 gene sequencer with genescan software (Applied Biosystems, Foster City, CA). Clonal rearrangements detected at presentation were looked for at week 20.

RESULTS

Of 42 patients, 35 had a clonal population detectable at presentation; of these, seven had more than two clonal rearrangements; this latter group showed a similar disease-free survival (DFS) to the group as a whole. Thirty of 35 patients were analyzed before their second course of intensification therapy at week 20. At this point, nine of 30 had a detectable clonal rearrangement, eight (89%) of whom have since relapsed with a median DFS of 27.5 months. Of the rest of the group (n=21), in whom no clonal rearrangement was detectable, only six (21%) have relapsed.

CONCLUSION

Fluorescent IgH PCR at week 20 provides a sensitive and specific means to predict ultimate relapse (57% and 89%, respectively) and is a simple yet promising technique for the identification of patients at risk of poor outcome.

A comparison of temperature in VLBW infants swaddled versus unswaddled in a double-walled incubator in skin control mode

PURPOSE

To determine differences in temperature for very low birth weight (VLBW) infants when swaddled and unswaddled in heated, double-walled incubators.

DESIGN

A crossover design was used with infants receiving both the swaddled and unswaddled conditions.

SAMPLE

15 very low birth weight infants (< 1,500 gms) with postconceptional ages of 29.1 +/- 1.5 weeks.

MAIN OUTCOME VARIABLE

Infant temperature in swaddled and unswaddled conditions.

RESULTS

Abdominal temperatures during swaddling were 0.2 degree C higher than the unswaddled condition. In the swaddled condition, infants required a lower incubator temperature (mean = 26.9 +/- 0.4) than when unswaddled (mean = 29.8 +/- 0.5).

The rapid diagnosis of acute promyelocytic leukaemia using PML (5E10) monoclonal antibody

Acute promyelocytic leukaemia (APL) is characterized cytogenetically by t(15;17)(q22:q21) which results in the production of a PML/RAR alpha fusion protein. Detection of the translocation or the fusion gene product is required for objective diagnosis of APL. This can be accomplished by conventional cytogenetic methods, fluorescence in situ hybridization or RT-PCR. Such techniques are time consuming and not universally available. The intracellular distribution of the PML protein in promyelocytes is characteristically altered in APL and this can be detected by immunocytochemistry. We have assessed two immunocytochemical methods, immunofluorescence and alkaline phosphatase-anti-alkaline phosphatase staining (APAAP), with regard to sensitivity, specificity and rapidity of diagnosis. 85 patients with AML including 15 cases of APL were studied. Immunofluorescence PML detection was concordant with RT-PCR for t(15:17) in 14/15 (93.3%) cases with no false positives. The negative APL case in our series was a patient with a 5' PML breakpoint who did not express the reciprocal t(17;15) fusion product. APAAP was concordant in only 6/13 (46%) APL cases with one false positive. In conclusion, immunofluorescent localization of PML using 5E10 monoclonal antibody is a rapid, sensitive and specific diagnostic tool for APL.

Detection and quantitation of the CBFbeta/MYH11 transcripts associated with the inv(16) in presentation and follow-up samples from patients with AML

We have developed a competitor-based RT-PCR technique which will detect and quantitate the CBFbeta/MYH11 transcripts associated with inv(16)(q22;p13) and have used it to study presentation and follow-up samples of acute myeloid leukaemia (AML). The levels of the leukaemia-specific transcripts are expressed as a ratio to a ubiquitously expressed mRNA species (Abl) which controls for RNA degradation. This technique has been applied to 75 consecutive patients presenting with either de novo AML or tMDS; 6/75 patients analysed were positive for the inv(16), all were confirmed by conventional cytogenetics. The inv(16) has a strong association with M4Eo, but we found only 2/6-positive patients to have this diagnosis (two patients with M2, one patient M1 and one patient had MDS). At presentation the levels of CBFbeta/MYH11 transcripts were 0.1-10/Abl transcript (mean 3.3/Abl transcript). Seventeen follow-up samples were available on 5/6 of these patients, and on two further patients in whom stored material was available. Following the first cycle of chemotherapy the level of transcripts was at least 10(-2) lower (0.1-10 x 10(-2)/abl transcript) than their presentation sample. Subsequent samples on these patients when in remission gave transcript levels in the range (1.0 x 10(-4) - 2 x 10(-3)/abl transcript), and three long-term follow-up samples were negative. We have developed a quantitative test which opens the possibility of predicting relapse by detecting changes in the numbers of leukaemia-specific transcripts.

The effects of swaddling versus standard positioning on neuromuscular development in very low birth weight infants

A randomized control design was used to compare the effect of swaddling to standard positioning on neuromuscular development in very low birth weight (VLBW) infants (< 1,250 gm). The outcome of neuromuscular development was measured at 34 weeks postconceptional age using the Morgan Neonatal Neurobehavioral Exam (MNNE). The sample included 50 infants who met criteria for birth weight, age and who were classified as appropriate for gestational age. Exclusion criteria were also used. The infants were randomly assigned to the experimental group or the comparison group. Data analysis included descriptive and inferential statistical techniques. The results demonstrated that swaddled infants had higher total scores on the MNNE as compared to infants with standard positioning. Swaddling appears to be a positioning technique that can enhance neuromuscular development of the very low birth weight infant.

32P-incorporation PCR for the detection of rearrangements at the TCR-gamma locus

We have adapted and developed a PCR (polymerase chain reaction)-based technique for the T-cell receptor (TCR)-gamma chain gene, which has subsequently been used for routine diagnosis. Variable-region oligonucleotide primers were chosen from subgroups I and II, and the joining region primer was from the J2 segment. The primers were used to perform a 32P-incorporation PCR, and the products were then separated on an 8% denaturing polyacrylamide gel. In our hands, this technique is more reliable than cold methods, when separation is performed on either agarose or nondenaturing polyacrylamide. The radioactive technique was used to look at 102 T-cell proliferations, of which eight of eight T-acute lymphoblastic leukemia (ALL), 24 of 34 T-non-Hodgkin's leukemia (NHL), and 35 of 60 large granular lymphocyte (LGL) expansions were clonal. Of 122 B-cell proliferations investigated, including 72 cases of B-cell lineage ALL, 36 demonstrated a T-cell rearrangement (33 ALLs and three myelomas). Samples from nonlymphoid tumors were tested and produced a normal distribution ladder of PCR products after autoradiography, a pattern also observed with antenatal and preoperative patients. The radiolabel-incorporation method detected an abnormal pattern of a ladder with prominent dark bands in 29 of 122 B-cell and 27 of 102 T-cell cases and in 0 of 49 of the nonlymphoid and normal samples. The abnormal banding patterns obtained in a proportion of the B- and T-cell cases was not readily discernible by nondenaturing-acrylamide or agarose-separation methods.