Individual Differences in Response to Sleep Deprivation: Assessment of Fatigue Following Sleep Loss

Previous work has indicated that a small but significant number of participants in sleep deprivation studies or in simulated shift work experiments manifests an exaggerated performance decrement when they reach a critical point in the experiment, usually near the trough of the circadian cycle or the middle of the night. Those who show this exaggerated response do not appear to differ from other non-nal volunteers in any substantial way according to usual screening criteria or baseline values. The present study aims to examine factors that may provide the basis for this extreme response. We propose that a preexisting sleep deficit-as manifested by low values on the Multiple Sleep Latency Test (MSLT)-may account for extreme responders. It has been shown that among normal volunteers screened for a variety of studies, approximately 20 to 25 percent show low ( 13 minutes). Additionally, studies by this group have indicated that subjects with low MSLT scores may suffer from chronic insufficient sleep, as further substantiated by the finding that they have consistently higher nocturnal sleep efficiency and that their MSLT scores rise to normal values when sleep is extended. We hypothesize that the short MSLT subjects have a significant long-term sleep deficit that leads to a marked intolerance for sleep deprivation or shift work. We further suggest that this sleep debt may signify an increased sleep need in these individuals that is not met either due to personal preference or to societal pressures (or both). If this speculation is accurate, then we predict that the tolerance for sleep deprivation in such individuals can be increased by "pretreatment" with sleep extension. Thus, the present study is designed to test the following two hypotheses: (1) subjects with nominal sleep patterns who have low MSLT scores (e.g., Sleepy subjects) will show an exaggerated response (performance decrement) to sleep loss compared to subjects who have high MSLT scores (Alert subjects) on a nominal sleep schedule; (2) when permitted to extend sleep--thus discharging their sleep debt-the Sleepy subjects will show a sleep-loss response resembling that of the Alert subjects

Individual Differences in Response to Sleep Deprivation: Assessment of Fatigue Following Sleep Loss

Previous work has indicated that a small but significant number of participants in sleep deprivation studies or in simulated shift work experiments manifests an exaggerated performance decrement when they reach a critical point in the experiment, usually near the trough of the circadian cycle or the middle of the night. Those who show this exaggerated response do not appear to differ from other non-nal volunteers in any substantial way according to usual screening criteria or baseline values. The present study aims to examine factors that may provide the basis for this extreme response. We propose that a preexisting sleep deficit-as manifested by low values on the Multiple Sleep Latency Test (MSLT)-may account for extreme responders. Roth and colleagues (1993) have shown that among normal volunteers screened for a variety of studies, approximately 20 to 25 percent show low ( 13 minutes). Additionally, studies by this group have indicated that subjects with low MSLT scores may suffer from chronic insufficient sleep (Roth et al., 1993), as further substantiated by the finding that they have consistently higher nocturnal sleep efficiency and that their MSLT scores rise to normal values when sleep is extended (Roehrs et al., 1996). We hypothesize that the short MSLT subjects have a significant long-term sleep deficit that leads to a marked intolerance for sleep deprivation or shift work. We further suggest that this sleep debt may signify an increased sleep need in these individuals that is not met either due to personal preference or to societal pressures (or both). If this speculation is accurate, then we predict that the tolerance for sleep deprivation in such individuals can be increased by "pretreatment" with sleep extension. Thus, the present study is designed to test the following two hypotheses: subjects with nominal sleep patterns who have low MSLT scores (e.g., Sleepy subjects) will show an exaggerated response (performance decrement) to sleep loss compared to subjects who have high MSLT scores (Alert subjects) on a nominal sleep schedule. when permitted to extend sleep-thus discharging their sleep debt-the Sleepy subjects will show a sleep-loss response resembling that of the Alert subjects

Developmental changes in sleep biology and potential effects on adolescent behavior and caffeine use

Adolescent development includes changes in the biological regulatory processes for the timing of sleep. Circadian rhythm changes and changes to the sleep-pressure system (sleep homeostasis) during adolescence both favor later timing of sleep. These changes, combined with prevailing social pressures, are responsible for most teens sleeping too late and too little; those who sleep least report consuming more caffeine. Although direct research findings are scarce, the likelihood of use and abuse of caffeine-laden products grows across the adolescent years due, in part, to excessive sleepines

Naps not as effective as a night of sleep at dissipating sleep pressure

The two-process model of sleep posits that two processes interact to regulate sleep and wake: a homeostatic (Process S) and a circadian process (Process C). Process S compensates for sleep loss by increasing sleep duration and intensity. Process C gates the timing of sleep/wake favouring sleep during the circadian night in humans. In this study, we examined whether taking six naps throughout a 24-hr period would result in the same amount of dissipation of homeostatic pressure at the end of the day as a night of sleep, when time in bed is equivalent. Data from 46 participants (10-23 years; mean = 14.5 [± 2.9]; 25 females) were analysed. Slow-wave energy, normalized to account for individual differences in slow-wave activity, was used as a measure of sleep homeostasis. In the nap condition, slow-wave energy of six naps distributed equally during a 24-hr period was calculated. In the baseline condition, slow-wave energy was measured after 9-hr time in bed. A paired t-test was used to compare nap and baseline conditions. A linear regression was used to examine whether slow-wave energy varied as a function of age. Slow-wave energy was greater during baseline than the nap condition (p < .001). No association between age and slow-wave energy was found for baseline or nap conditions. Our findings indicate that multiple naps throughout the day are not as effective at dissipating sleep pressure as a night of sleep. This is likely due to the influence of the circadian system, which staves off sleep during certain times of the day

Keeping an Eye on Circadian Time in Clinical Research and Medicine

Background: Daily rhythms are observed in humans and almost all other organisms. Most of these observed rhythms reflect both underlying endogenous circadian rhythms and evoked responses from behaviours such as sleep/wake, eating/fasting, rest/activity, posture changes and exercise. For many research and clinical purposes, it is important to understand the contribution of the endogenous circadian component to these observed rhythms. Content: The goal of this manuscript is to provide guidance on best practices in measuring metrics of endogenous circadian rhythms in humans and promote the inclusion of circadian rhythms assessments in studies of health and disease. Circadian rhythms affect all aspects of physiology. By specifying minimal experimental conditions for studies, we aim to improve the quality, reliability and interpretability of research into circadian and daily (i.e., time-of-day) rhythms and facilitate the interpretation of clinical and translational findings within the context of human circadian rhythms. We describe protocols, variables and analyses commonly used for studying human daily rhythms, including how to assess the relative contributions of the endogenous circadian system and other daily patterns in behaviours or the environment. We conclude with recommendations for protocols, variables, analyses, definitions and examples of circadian terminology.Conclusion: Although circadian rhythms and daily effects on health outcomes can be challenging to distinguish in practice, this distinction may be important in many clinical settings. Identifying and targeting the appropriate underlying (patho)physiology is a medical goal. This review provides methods for identifying circadian effects to aid in the interpretation of published work and the inclusion of circadian factors in clinical research and practice

Relationship of Morning Cortisol to Circadian Phase and Rising Time in Young Adults with Delayed Sleep Times

The present study was aimed at further elucidating the relationship between circadian phase, rising time, and the morning cortisol awakening response (CAR). The results presented here are a secondary analysis of experimental data obtained from a study of advanced sleep-wake schedules and light exposures on circadian phase advances measured by dim-light melatonin onset (DLMO). The present results demonstrate that morning CAR is strongly related to rising time and more weakly related to DLMO phase

Acute Changes in Sleep Duration on Eating Behaviors and Appetite-Regulating Hormones in Overweight/Obese Adults

There is considerable interest in the role of sleep in weight regulation, yet few studies have examined this relationship in overweight/obese (OW/OB) adults. Using a within-subject, counterbalanced design, 12 OW/OB women were studied in lab with two nights of short (5 hr time in bed [TIB]) and two nights of long (9 hr TIB) sleep. Hunger, consumption at a buffet, and fasting hormone levels were obtained. Significant polysomnographic differences occurred between conditions in total sleep time and sleep architecture (ps < .001). Percent energy from protein at the buffet increased following short sleep. No differences were observed for total energy intake or measured hormones. Further research is needed to determine how lengthening sleep impacts weight regulation in OW/OB adults

Genome-wide DNA methylation patterns associated with sleep and mental health in children: a population-based study

Background: DNA methylation (DNAm) has been implicated in the biology of sleep. Yet, how DNAm patterns across the genome relate to different sleep outcomes, and whether these associations overlap with mental health is currently unknown. Here, we investigated associations of DNAm with sleep and mental health in a pediatric population. Methods: This cross-sectional study included 465 10-year-old children (51.3% female) from the Generation R Study. Genome-wide DNAm levels were measured using the Illumina 450K array (peripheral blood). Sleep problems were assessed from self-report and mental health outcomes from maternal questionnaires. Wrist actigraphy was used in 188 11-year-old children to calculate sleep duration and midpoint sleep. Weighted gene co-expression network analysis was used to identify highly comethylated DNAm ‘modules’, which were tested for associations with sleep and mental health outcomes. Results: We identified 64 DNAm modules, one of which associated with sleep duration after covariate and multiple testing adjustment. This module included CpG sites spanning 9 genes on chromosome 17, including MAPT – a key regulator of Tau proteins in the brain involved in neuronal function – as well as genes previously implicated in sleep duration. Follow-up analyses suggested that DNAm variation in this region is under considerable genetic control and shows strong blood–brain concordance. DNAm modules associated with sleep did not overlap with those associated with mental health. Conclusions: We identified one DNAm region associated with sleep duration, including genes previously reported by recent GWAS studies. Further research is warranted to examine the functional role of this region and its longitudinal association with sleep

The impact of sleep and psychiatric symptoms on alcohol consequences among young adults

OBJECTIVE: Independent lines of research have documented links between psychiatric symptoms and poor sleep quality, psychiatric symptoms and alcohol use, and alcohol use and poor sleep quality. The current study examined the synergistic effect of poor sleep quality and psychiatric symptoms on alcohol-related consequences in heavy-drinking young adults. METHOD: Matriculating college students reporting at least one heavy drinking episode over the first nine weeks of the semester (N = 385, 52% female) were categorized as experiencing ‘good’ (n = 280) versus ‘poor’ sleep quality (n = 105) and screening ‘positive’ (n = 203) or ‘negative’ (n = 182) for a psychiatric disorder. Sleep quality was assessed using the Pittsburgh Sleep Quality Index; psychiatric diagnosis was assessed using the Psychiatric Diagnostic Screening Questionnaire; and alcohol-related consequences were assessed using the Brief Young Adult Alcohol Consequences Questionnaire. General linear models were used to examine the main effects and interaction between sleep quality and psychiatric symptoms on alcohol-related consequences. RESULTS: Sleep quality moderated the association between psychiatric screen and alcohol-related consequences among heavy-drinking college students, such that psychiatric symptoms were associated with more alcohol-related consequences in the context of poor sleep quality. CONCLUSIONS: The combination of poor sleep quality and psychiatric symptoms is associated with increased alcohol-related consequences among heavy-drinking college students. Given the significant interaction between these symptoms, healthcare providers are encouraged to screen for the presence of sleep and psychiatric disorders among heavy-drinking young adults and to provide empirically-supported treatments as appropriate