Accumulated Sleep Debt Research Articles

The Circadian Brain and Cognition.

Circadian rhythms are inherent to living organisms from single cells to humans and operate on a genetically determined cycle of approximately 24hours. These endogenous rhythms are aligned with the external light/dark cycle of the Earth's rotation and offer the advantage of anticipating environmental changes. Circadian rhythms act directly on human cognition and indirectly through their fundamental influence on sleep/wake cycles. The strength of the circadian regulation of performance depends on the accumulated sleep debt and the cognitive domain, and it has been suggested to involve the activation of ascending arousal systems and their interaction with attention and other cognitive processes. In addition, attention-related cortical responses show extensive circadian rhythms, the phases of which vary across brain regions. This review discusses the impact of the circadian system on sleep/wake regulation and cognitive performance. It further addresses the health implications of circadian disruption, particularly in relation to mental and neurological disorders.

Prevalence, correlates, and mental health outcomes of social jetlag in Chinese school-age adolescents: A large-scale population-based study

BackgroundThis cross-sectional study aimed to examine the prevalence and correlates of social jetlag (SJL) in Chinese adolescents, as well as to test the relationships between SJL and mental health problems. MethodsA total of 106979 students (Mage = 13.0 ± 1.8 years; Nmale = 58296 [54.5 %]) from Shenzhen, China completed an online survey from May 24th to June 5th, 2022. Information on sociodemographics, lifestyles, sleep characteristics, anxiety symptoms, and depressive symptoms was collected by a self-administered questionnaire. Multivariate and binary logistic regression were adopted for data analysis. Results17.8 % of participants experienced SJL ≥ 2 h. To adjust the accumulated sleep debt, sleep-corrected SJL (SJLsc) was calculated and 8.3 % of individuals self-reported SJLsc ≥ 2 h. Both SJL and SJLsc show an increasing trend with age. Risk factors of SJL included females, poor parental marital status, being overweight, physically inactive, smoking, drinking, and having a late chronotype. Moreover, males, having siblings, boarding at school, short sleep duration, experiencing insomnia, and frequent nightmares were significantly associated with an increased risk of SJLsc. After adjusting for all covariates, adolescents with SJLsc ≥ 2 h were more likely to have anxiety symptoms (OR: 1.35, 95 % CI: 1.24–1.48) and depressive symptoms (OR: 1.35, 95 % CI: 1.25–1.46) than those with SJLsc < 1 h. ConclusionsSJL is common among Chinese school-age adolescents. This study is valuable for the development of prevention and intervention strategies for SJL in adolescents at the population level. Additionally, the strong links between SJLsc and emotional problems underscore the critical significance of addressing SJL as a key aspect of adolescent well-being.

Effects of Chronotype and Social Jet-Lag on Neurocognitive Functioning

The chronotype, which reflects the circadian rhythm preferences of individuals in their daily activities and sleep-wake cycles, can be considered on a dimension of extreme morningism and extreme eveningism. Individuals with extreme morning and extreme evening chronotypes face many physical and psychological dangers due to accumulated sleep debt, short total sleep time and insufficient sleep efficiency. In extreme chronotypes, especially in extreme evening people, the social jet-lag effect due to the mismatch between social and circadian clocks is thought to exacerbate these dangers. More recent studies have suggested that social jet-lag and chronotype have many negative effects on cognitive functioning. The aim of this article is to review the impact of social jet-lag and chronotype on cognitive functioning.

Validity of the Persian version of the Munich ChronoType Questionnaire (MCTQIR).

Currently, the most useful questionnaire for determining the chronotype is the Munich ChronoType Questionnaire (MCTQ). It determines chronotype based on sleep-wake behavior on workdays and work-free days and uses the mid-sleep time on free days (MSF), corrected for accumulated sleep debt over the work week to classify chronotype (MSFsc). Our study aimed at validating Persian version of the MCTQ. Participants completed the Persian version of the MCTQ, reduced Morningness-Eveningness Questionnaire (rMEQ), Epworth sleepiness scale (ESS), and demographic characteristics. Thestudy sample was comprised of 250 Iranian men and women (mean age 34 years, age range 30 to 58 years, 113 men). Results showed that there is a significant negative relationship between the components of MCTQ and rMEQ, and the strongest relationship related to the MSF index. The results alsoshowed that MCTQ parameters were not significantly related to the ESS scale. Cut-off values of MSFsc for chronotype categories were determined by inter-quartile range (Q25% = 3.44, Q50% = 4.68, and Q75% = 5.75). Like the MCTQ in other languages, the Persian version of the MCTQ is a reliable tool for assessing chronotype.

Association Between Nap and Reported Cognitive Function and Role of Sleep Debt: A Population-Based Study.

The relationship between napping and cognition remains controversial. This study aimed to investigate the association between napping and cognition according to sleep debt in the Korean adult population.A population-based nationwide cross-sectional survey was conducted in 2018. A two-stage stratified random sample of Koreans aged ≥19 years was selected and evaluated using questionnaires by trained interviewers. Cognitive function was assessed using the Mail-In Cognitive Function Screening Instrument (MCFSI). Sleep habits on weekdays and weekends, napping, and subjective sleep requirements were assessed using the questionnaires. Accumulated sleep debt was calculated by subtracting the weekly average sleep duration from subjective sleep requirements. Sleep quality, daytime sleepiness, insomnia, depression, demographics, and comorbidities were assessed. Participants were grouped into those with sleep debt ≤60 min and those with sleep debt >60 min. Multiple linear regression was used to estimate the independent association between the factors and cognition.In total, 2,501 participants were included in the analysis. Naps were reported in 726 (29.0%) participants (nappers). The mean MCFSI score was higher in nappers (3.4±3.6) than in non-nappers (2.3±3.0) (p<0.001). Multiple linear regression controlling for age, alcohol, smoking, depression, insomnia, daytime sleepiness, sleep quality, and education revealed that 30 to 60 min of napping was associated with worse cognitive function in participants with sleep debts ≤60 min, while >60 min of napping was associated with better cognitive function in participants with sleep debts >60 min.In general, naps are associated with worse cognitive function in the Korean adult population. However, for those with sleep debt of >60 min, naps for >60 min were associated with better cognitive function.

Association Between Nap and Reported Cognitive Function and Role of Sleep Debt: A Population-Based Study.

Background and PurposeThe relationship between napping and cognition remains controversial. This study aimed to investigate the association between napping and cognition according to sleep debt in the Korean adult population.MethodsA population-based nationwide cross-sectional survey was conducted in 2018. A two-stage stratified random sample of Koreans aged ≥19 years was selected and evaluated using questionnaires by trained interviewers. Cognitive function was assessed using the Mail-In Cognitive Function Screening Instrument (MCFSI). Sleep habits on weekdays and weekends, napping, and subjective sleep requirements were assessed using the questionnaires. Accumulated sleep debt was calculated by subtracting the weekly average sleep duration from subjective sleep requirements. Sleep quality, daytime sleepiness, insomnia, depression, demographics, and comorbidities were assessed. Participants were grouped into those with sleep debt ≤60 min and those with sleep debt >60 min. Multiple linear regression was used to estimate the independent association between the factors and cognition.ResultsIn total, 2,501 participants were included in the analysis. Naps were reported in 726 (29.0%) participants (nappers). The mean MCFSI score was higher in nappers (3.4±3.6) than in non-nappers (2.3±3.0) (p<0.001). Multiple linear regression controlling for age, alcohol, smoking, depression, insomnia, daytime sleepiness, sleep quality, and education revealed that 30 to 60 min of napping was associated with worse cognitive function in participants with sleep debts ≤60 min, while >60 min of napping was associated with better cognitive function in participants with sleep debts >60 min.ConclusionsIn general, naps are associated with worse cognitive function in the Korean adult population. However, for those with sleep debt of >60 min, naps for >60 min were associated with better cognitive function.

The COVID-19 Lockdown and Changes in Routine-Oriented Lifestyle Behaviors and Symptoms of Depression, Anxiety, and Insomnia in South Africa.

The authors assessed the impact of lockdown in response to the COVID-19 pandemic on routine-oriented lifestyle behaviors and symptoms of depression, anxiety, and insomnia in South Africans. In this observational study, 1048 adults (median age = 27y; n = 767 females; n = 473 students) responded to an online survey on work, exercise, screen, alcohol, caffeine and sleep behaviors, depression, anxiety, and insomnia before and during lockdown. Comparisons were made between males and females, and students and nonstudents. During lockdown, males reported larger reductions in higher intensity exercise and alcohol use than females, while depressive symptoms increased more among females, more of whom also reported poorer sleep quality. Students demonstrated larger delays in work and sleep timing, greater increases in sitting, screen, sleep duration, napping, depression and insomnia and larger decreases in work hours, exercise time, and sleep regularity compared with nonstudents. Students experienced more changes in their routine-oriented behaviors than nonstudents, coupled with larger increases in depression and insomnia. The dramatic change in their work and sleep timing suggests habitual routines that are at odds with their chronotype, with their sleep changes during lockdown likely reflecting "catch-up" sleep in response to accumulated sleep debt under usual routines.

False-positive cases in multiple sleep latency test by accumulated sleep debt.

PurposeMultiple sleep latency test (MSLT) is performed as objective assessment of sleepiness, on the following day after polysomnography (PSG). In most clinics, patients are required to stay for 2 days. However, if patients have chronic sleep debt before the examination, even if they get adequate nocturnal sleep during the initial PSG, their sleep debt would not be fully resolved, affecting MSLT results. This may lead to improper administration of psycho‐stimulant medication. To clarify the sleep debt for the patients who showed short sleep latencies, we compared the mean sleep latencies of MSLTs.MethodsTwelve hypersomnolent males, who underwent MSLTs (1st MSLT with 1 night and 2nd MSLT with more than 3 nights), were enrolled. We selected these cases based on the longer total sleep time on PSG night compared to the mean total sleep time on pre‐examination sleep logs and shortened sleep latencies on PSG. To evaluate the effect of the sleep debt for the patients who showed short sleep latencies, we extended their hospitalization or re‐hospitalized them.ResultsThe mean sleep latency of 1st MSLT was 5.8 minutes and that of 2nd was 13.9 minutes (P < .001). Among these 12 cases, 5 cases altered from short to normal sleep latencies at the 2nd MSLT. These 5 cases were prevented from over‐diagnoses by the extension of evaluations.ConclusionsThe sleep debt may produce false‐positive results when patients are examined by standard PSG and MSLT. Accumulation of sleep debt will cause shortened sleep latencies in the following nights. Patients should be advised to extend their hospitalization before PSG and MSLT to reduce the chronic sleep debt for accurate diagnosis of hypersomnia.

The effects of the number of consecutive night shifts on sleep duration and quality.

Objectives:The organization of night shift work affects sleep duration and quality. The aim of this study was to investigate the effects of the number of consecutive night shifts on sleep duration and quality among police officers with night shift work as part of their normal schedule.Methods:This quasi-experimental, within-subject crossover study included 73 police officers. All participants performed three work schedules: two, four and seven consecutive night shifts followed by the same number of recovery days, ie, day work or days off (2+2, 4+4, and 7+7). Sleep assessed through sleep diaries and actigraphy after all night shifts and recovery days (totaling 26 days) was compared by use of repeated measures analysis.Results:Participants experienced shorter sleep duration (with and without naps), more premature awakening, less difficulty falling asleep, and more non-refreshing sleep after night shifts compared with recovery days. Sleep duration and quality did not change with increasing number of consecutive night shifts. Sleep was shorter and of poorer quality after the last night shift in the 2+2 and 4+4 work schedule compared with the second and fourth night shift, respectively, in the 7+7 schedule.Conclusion:Sleep duration was reduced after night shift work and did not increase with more consecutive night shifts, which leads to accumulated sleep debt. Sleep duration was shortest and sleep quality was poorest after the last night shift in a series of night shifts.

Practical applications of circadian science in adolescents

Two studies published in this volume in The Journal highlight the contribution of circadian rhythms to seemingly disparate aspects of health in adolescents: driving safety and glycemic control. Both studies appropriately take into account sleep duration as necessary, but not sufficient, to explore the relationship of sleep with these topics. Owens et al determined that for a cohort of teen drivers, not only was shorter sleep duration associated with drowsy driving, but also a more pronounced “night owl” tendency, or evening chronotype. Simon et al found that in their sample of teens who were overweight/obese, shorter sleep duration, later bedtimes, and later circadian timing of sleep were associated with more pronounced insulin resistance. Borbely's classic model of sleep hypothesizes regulation by both sleep-wake homeostasis (accumulated sleep debt, or process S) and circadian process C (Hum Neurobiol 1982;1:195-204). There are different ways to assess circadian rhythms. Owens et al used a morningness-eveningness questionnaire to assess preferred times for different activities for their larger cohort. Simon et al used salivary melatonin onset and offset in dim light conditions in comparison with actigraphy data to measure the alignment of circadian sleep timing vs actual sleep timing. Circadian timing and alignment have implications for both public health and physiology. The processes are intertwined (J Sleep Res 2016;25:131-43). Per Owens et al, the emerging concept of sleep deficiency incorporates both circadian misalignment as well as inadequate sleep time. The reverse of sleep deficiency may be the more positive concept of sleep health. Ultimately, a simple public health intervention—later school start times, leading to increased and more appropriately timed sleep—may address both the risk of automotive accidents and endocrinologic impairment as documented here (Pediatrics 2014;134:642-9). But simple isn't always easy. As grade schools here in Central Virginia1Remmers V. After police were called four times for missing children on buses, questions linger for Chesterfield parents about transportation issues.https://www.richmond.com/news/local/education/chesterfield/after-police-were-called-four-times-for-missing-children-on/article_195a6958-6ec7-5bcc-8da3-d7e70effadb9.htmlDate: 2018Google Scholar, 2Remmers V. What happened with Chesterfield's school buses? Officials offer some answers.https://www.richmond.com/news/local/chesterfield/what-happened-with-chesterfield-s-school-buses-officials-offer-some/article_0c794a32-8d48-5185-86e6-376d45cc4bd2.htmlDate: 2018Google Scholar and elsewhere struggle with transitions to earlier start times to accommodate later high school start times, these articles can remind us what is at stake. Articles pages 224 and 257 ▶ Drowsy Driving, Sleep Duration, and Chronotype in AdolescentsThe Journal of PediatricsVol. 205PreviewTo determine whether self-reported drowsy driving was associated with an evening chronotype, a biologically-based difference in circadian sleep-wake timing, and shorter school-night sleep duration in a sample of high school drivers. Full-Text PDF Too Late and Not Enough: School Year Sleep Duration, Timing, and Circadian Misalignment Are Associated with Reduced Insulin Sensitivity in Adolescents with Overweight/ObesityThe Journal of PediatricsVol. 205PreviewTo examine the relationship between insulin resistance (IR) and sleep/circadian health in overweight/obese adolescents. We hypothesized that insufficient and delayed sleep would be associated with IR in this population. Full-Text PDF

Validation of the Korean Munich Chronotype Questionnaire.

The Munich Chronotype Questionnaire (MCTQ) assesses actual sleep-wake timing and has advantages compared to prior chronotype questionnaires in that it differentiates sleep-wake patterns between work days and free days and uses corrected mid-sleep time on free days after correcting for accumulated sleep debt over the week to categorize chronotype. The current study, we validated the Korean version of the MCTQ. In this study, 310 participants (mean age = 27.09 ± 5.64; 78.1% females) completed the Korean version of the MCTQ. MCTQ parameters were significantly correlated with MEQ (Morningness-Eveningness Questionnaire) scores (│r│ ≥ 0.48), and test-retest reliability was ≥ 0.72. Cutoff scores of 2.5%, which correlated to 2.36 and 8.57 mid-sleep times in our sample, showed the best convergence with MEQ when categorizing chronotype. Our study suggests that the MCTQ is a useful questionnaire in assessing chronotype in young adults.

Effects of sleep disruption and high fat intake on glucose metabolism in mice

Poor sleep quality or quantity impairs glycemic control and increases risk of disease under chronic conditions. Recovery sleep may offset adverse metabolic outcomes of accumulated sleep debt, but the extent to which this occurs is unclear. We examined whether recovery sleep improves glucose metabolism in mice subjected to prolonged sleep disruption, and whether high fat intake during sleep disruption exacerbates glycemic control. Adult male C57BL/6J mice were subjected to 18-h sleep fragmentation daily for 9 days, followed by 1 day of recovery. During sleep disruption, one group of mice was fed a high-fat diet (HFD) while another group was fed standard laboratory chow. Insulin sensitivity and glucose tolerance were assessed by insulin and glucose tolerance testing at baseline, after 3 and 7 days of sleep disruption, and at the end of the protocol after 24h of undisturbed sleep opportunity (recovery). To characterize changes in sleep architecture that are associated with sleep debt and recovery, we quantified electroencephalogram (EEG) recordings during sleep fragmentation and recovery periods from an additional group of mice. We now report that 9 days of 18-h daily sleep fragmentation significantly reduces rapid eye movement sleep (REMS) and non-rapid eye movement sleep (NREMS). Mice respond with increases in REMS, but not NREMS, during the daily 6-h undisturbed sleep opportunity. However, both REMS and NREMS increase significantly during the 24-h recovery period. Although sleep disruption alone has no effect in this protocol, high fat feeding in combination with sleep disruption impairs glucose tolerance, effects that are reversed by recovery sleep. Insulin sensitivity modestly improves after 3 days of sleep fragmentation and after 24h of recovery, with significantly greater improvements in mice exposed to HFD during sleep disruption. Improvements in both glucose tolerance and insulin sensitivity are associated with NREMS rebound, raising the possibility that this sleep phase contributes to restorative effects of recovery sleep on glycemic control.

Sleep recovery in participants after racing in the Finnmarkslop - Europe's longest dog‑sled race.

During the dog-sled race, the Finnmarkslop (FL), which lasts up to 7 days, participants get little sleep and what they get is fragmented; concerns have been raised about proper sleep recovery. The aim of this study was to examine awareness of sleep deprivation by FL participants and post-race sleep recovery after completion of the race. A total of 55 participants responded to an online survey 1 week and 1 month after the race; this measured the following factors: their awareness of sleep loss and possible strategies for recovery; their sleep-wake patterns using a Pittsburgh Sleep Questionnaire Index; and possible changes in respondents' sleep-wake patterns compared with their regular routines. During the FL, participants slept about 3-4 hours a day. Many were not aware of the accumulated sleep debt and did not engage in strategies to make up the loss. Insufficient levels of sleep and impoverished sleep quality were observed after the race, especially among those who were engaged in the FL for a longer period. Alertness levels were affected 1 week after the race. Among participants in the FL, the lack of awareness of sleep debt and insufficient sleep recovery could lead to health consequences. Those engaged in the race for longer should be more cautious during the recovery process because of possible sleep problems occurring after the race. Educational campaigns and easy access to professional support should be provided for participants in this type of sporting event.

Sleep Duration in Rough Sea Conditions.

Environmental motion can affect shipboard sleep of crewmembers. Slamming and similar harsh motion may interfere with sleep, whereas mild motion and sopite syndrome may enhance sleep. If sleep needs vary by sea condition, this factor should be considered when assessing human performance at sea. The goal of this study was to assess sleep duration in different sea conditions. Crewmembers (N = 52) from a U.S. Navy vessel participated in the study while performing their normal daily schedule of duties. Sleep was assessed with wrist-worn actigraphy. Motion sickness and sopite syndrome were assessed using standardized questionnaires. In rough sea conditions, crewmembers experienced increased severity of motion sickness and sopite syndrome compared to their ratings during calmer sea conditions. Crewmembers slept significantly longer during sea state 5-6 compared to sleep on days with sea state 4 (25% increase) and sea state 3-4 (30% increase). Specifically, daily sleep increased from 6.97 ± 1.24 h in sea state 3-4, to 7.23 ± 1.65 h in sea state 4, to 9.04 ± 2.90 h in sea state 5-6. Although the duration of sleep in rough seas increased significantly compared to calmer sea conditions, causal factors are inconclusive. Accumulated sleep debt, motion-induced fatigue, and sopite syndrome all may have contributed, but results suggest that motion sickness and sopite syndrome were the predominant stressors. If sleep needs increase in severe motion environments, this factor should be taken into account when developing daily activity schedules or when modeling manning requirements on modern ships.

Rapid Changes in Scores on Principal Components of the EEG Spectrum do not Occur in the Course of “Drowsy” Sleep of Varying Length

Wakefulness is separated from a well-established sleep by an onset period. This is characterized by dramatic changes in scores on the first and second principal components of the electroencephalographic (EEG) spectrum, which reflects the kinetics of sleep- and wake-promoting processes. The present analysis examined whether significant buildups and declines of the first and second scores can occur throughout stage 1 sleep, or only on its boundaries with stage 2 and wakefulness. Twenty-seven adults participated in multiple 20-minute attempts to nap in the course of 24-hour wakefulness after either deprivation, restriction or ad lib night sleep. Power spectra were calculated on 1-minute intervals of 251 EEG records. Irrespective of accumulated sleep debt and duration of stage 1 sleep (from <2 to >5 minutes), the first principal component score was permanently attenuated across this stage as well as during preceding wakefulness. It showed rapid buildup only on the boundary with stage 2. The second principal component score always started its decline earlier, on the wake-sleep boundary. It did not show further decline throughout the following intervals of stages 1 and 2. It seems that stage 1 sleep occurs due to a delay of the buildup of the sleep-promoting process relative to the decline of the wake-promoting process which coincide, with initiation of stage 2 sleep and termination of wakefulness. Therefore, "drowsy" sleep can be regarded as occupying "no man's land", between the opponent driving forces for wake and sleep.

An Unusual Pattern of CPAP Usage

An Unusual Pattern of CPAP Usage

Long‐term synaptic plasticity is impaired in rats with lesions of the ventrolateral preoptic nucleus

Impairment of memory functions has been frequently reported in models of sleep deprivation. Similarly, hippocampal long-term synaptic plasticity has been shown to be sensitive to sleep loss caused by acute sleep restriction. However, such approaches are limited by the stressful nature of sleep deprivation, and because it is difficult to study long-term sleep restriction in animals. Here, we report the effects of chronic sleep loss on hippocampal long-term potentiation (LTP) in a rodent model of chronic partial sleep deprivation. We studied LTP of the Schaffer collateral-CA1 synapses in hippocampal slices prepared from rats with lesions of the ventrolateral preoptic nucleus (VLPO), which suffered reductions in total sleep time for several weeks after lesions. In slices prepared from VLPO-lesioned rats, LTP was impaired proportionally to the amount of sleep loss, and the decline in LTP followed a single exponential function over the amount of accumulated sleep debt. As compared with sham-lesioned controls, hippocampal slices from VLPO-lesioned rats showed a greater response to adenosine antagonists and greater paired-pulse facilitation (PPF). However, exogenous adenosine depressed evoked synaptic transmission and increased PPF in VLPO-lesioned and sham-lesioned rats by equal amounts, suggesting that the greater endogenous adenosine inhibitory tone in the VLPO-lesioned rats is associated with greater ligand accumulation rather than a change in adenosine receptor sensitivity or adenosine-mediated neurotransmitter release probability. LTP in VLPO-lesioned animals was partially restored by adenosine antagonists, suggesting that adenosine accumulation in VLPO-lesioned animals could account for some of the observed synaptic plasticity deficits.

Driver fatigue: The importance of identifying causal factors of fatigue when considering detection and countermeasure technologies

Driver fatigue is an ill-defined term in the literature. It has been broadly used to refer to a wide range of driver states, each with different causal mechanisms. Technologies currently exist which enable detection of driver fatigue and interventions that have the potential to dramatically reduce crash probability. The successful implementation of these technologies depends on the cause and type of fatigue experienced. Sleep-related (SR) forms of driver fatigue result from accumulated sleep debt, prolonged wakefulness or troughs in the circadian rhythms. SR fatigue is resistant to most intervention strategies. Conversely, technologies for detecting and countering task-related (TR) fatigue (caused by mental overload or underload) are proving to be effective tools for improving transportation safety. Methods of detecting and counteracting the various forms of driver fatigue are discussed. Emphasis is placed on examining the effectiveness of existing and emerging technologies for combating TR forms of driver fatigue.

The Multiple Sleep Latency Test in the Diagnosis of Narcolepsy

Back to table of contents Previous article Next article Letter to the EditorFull AccessThe Multiple Sleep Latency Test in the Diagnosis of NarcolepsyMICHAEL RACK, M.D., JAMES DAVIS, M.D., HOWARD P. ROFFWARG, M.D., ALLEN RICHERT, M.D., and ALP S. BARAN, M.D., MICHAEL RACKSearch for more papers by this author, M.D., JAMES DAVISSearch for more papers by this author, M.D., HOWARD P. ROFFWARGSearch for more papers by this author, M.D., ALLEN RICHERTSearch for more papers by this author, M.D., and ALP S. BARANSearch for more papers by this author, M.D., Jackson, Miss.Published Online:1 Nov 2005https://doi.org/10.1176/appi.ajp.162.11.2198-aAboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail To the Editor: We read with interest the clinical case conference by Lois E. Krahn, M.D., and Heydy L. Gonzalez-Arriaza, M.D. (1). Excessive daytime sleepiness is a common symptom of many sleep disorders, including narcolepsy. It can be difficult to make a firm diagnosis of narcolepsy, especially when the pathognomonic symptom of cataplexy is absent. Even when present, cataplexy rarely occurs in a physician’s office. As mentioned by the authors, some drug abusers fabricate sleep symptoms to obtain psychostimulants.Although narcolepsy cannot be diagnosed based on the Multiple Sleep Latency Test alone, a properly performed Multiple Sleep Latency Test can help to confirm the diagnosis (2). Drs. Krahn and Gonzalez-Arriaza discussed some of the challenges of performing the Multiple Sleep Latency Test in a suspected narcoleptic patient. For example, in the excellent case presented, the authors appropriately adjusted the timing of the Multiple Sleep Latency Test and the preceding polysomnogram to accommodate the patient’s delayed sleep phase (3). However, their patient also had a short habitual total sleep time of approximately 5 hours, as documented by 1 week of wrist actigraphy. The fact that the patient was able to obtain 7.2 hours of sleep during the nocturnal polysomnogram suggests that he may have insufficient sleep syndrome, possibly associated with inadequate sleep hygiene.At the University of Mississippi Sleep Disorders Center, we emphasize to our patients the importance of allowing sufficient time for sleep by spending at least 8 hours per night in bed in the week preceding a Multiple Sleep Latency Test. Usually a sleep log is used to document the preceding week’s sleep. We commend the authors on the use of more objective wrist actigraphy, which documented a chronically insufficient sleep time but question assigning the diagnosis of narcolepsy to a patient with apparent chronically insufficient sleep.As Drs. Krahn and Gonzalez-Arriaza illustrated in this case, the diagnosis of narcolepsy must be based on a combination of history, examination, and overnight polysomnogram findings, in addition to the Multiple Sleep Latency Test. As is known, the results of a Multiple Sleep Latency Test are influenced by the quantity and quality of the preceding 7 nights of sleep (3). Chronic sleep deprivation can mimic narcolepsy on a Multiple Sleep Latency Test. Accordingly, we wonder about the possibility that the Multiple Sleep Latency Test results in the case presented were affected by an accumulated sleep debt that could not be more than partially compensated for by the 7.2 hours of nocturnal sleep preceding the test.

Sleep homeostasis in suprachiasmatic nuclei-lesioned rats: effects of sleep deprivation and triazolam administration

The electroencephalogram (EEG) and electromyogram of rats with lesions in the suprachiasmatic nuclei (SCNx) were recorded during two series of 24-h baseline, 6-h sleep deprivation (SD), and 24-h recovery. At recovery onset, rats were injected i.p. with vehicle (VEH) control solution or 0.4 mg/kg triazolam (TRZ) in a balanced crossover design. Consecutive 10-s epochs were scored for vigilance states and EEG power spectra were computed. Arousal states were uniformly distributed during 24-h baseline (wake 47% of recording time, non-rapid-eye movement sleep (nonREMS) 47%, REMS 7%), and EEG spectra (0–25 Hz) were devoid of significant trends. State-specific EEG power spectra profiles in SCNx rats were similar to those of intact animals reported previously. However, EEG delta power (0.5–3.5 Hz_ of nonREMS was markedly lower in SCNx rats. Recovery from 6-h SD was characterised by a short-lasting reduction of REMS, and a long-lasting increase of nonREMS time of the cost of wakefulness. EEG delta power rebounded during the first 8 h in recovery, and fell below baseline level after 12 h in recovery. During 0–2 h TRZ recovery, rats spent more time in nonREMS with higher EEG slow wave activity as compared to the corresponding VEH recovery period. EEG slow wave activity fell below basel levels 10 h after TRZ injection and termination of SD. We conclude that major features of homeostatic sleep EEG regulation are present in SCNx rats. As opposed to an experiment with non-sleep-deprived SCNx rats reported previously. TRZ did induce sleep in the present experiment supporting our earlier hypothesis that benzodiazepine-induced sleep is dependent upon accumulated sleep debt.