Detection of human drowsiness by the vestibulo-ocular reflex compensating for heartbeat-induced head perturbations.

The vestibulo-ocular reflex (VOR) stabilizes vision during head movements by counter-rotating the eyes in the orbits. Although considered one of the simplest reflexes due to its minimal neuronal circuity comprising a 3-neuron arc, previous studies have shown that VOR performance deteriorates in both monkeys and humans when they are drowsy. Given constant head perturbations under dynamic environments, the VOR has been proposed as a viable biomarker for detecting human drowsiness in automobiles and other moving vehicles. However, under stationary environments where exogenous head movements are absent, its applicability has been questioned. In this study, we demonstrate that each heartbeat generates small yet distinctive head movements, and the VOR compensates for these minor head perturbations. Furthermore, we show that the effectiveness of VOR responses varies with the degree of drowsiness, indicating that the VOR can serve as an indicator of drowsiness, even in stationary contexts such as in classrooms and offices.

Morning resting hypothalamus-dorsal striatum connectivity predicts individual differences in diurnal sleepiness accumulation.

While the significance of obtaining restful sleep at night and maintaining daytime alertness is well recognized for human performance and overall well-being, substantial variations exist in the development of sleepiness during diurnal waking periods. Despite the established roles of the hypothalamus and striatum in sleep-wake regulation, the specific contributions of this neural circuit in regulating individual sleep homeostasis remain elusive. This study utilized resting-state functional magnetic resonance imaging (fMRI) and mathematical modeling to investigate the role of hypothalamus-striatum connectivity in subjective sleepiness variation in a cohort of 71 healthy adults under strictly controlled in-laboratory conditions. Mathematical modeling results revealed remarkable individual differences in subjective sleepiness accumulation patterns measured by the Karolinska Sleepiness Scale (KSS). Brain imaging data demonstrated that morning hypothalamic connectivity to the dorsal striatum significantly predicts the individual accumulation of subjective sleepiness from morning to evening, while no such correlation was observed for the hypothalamus-ventral striatum connectivity. These findings underscore the distinct roles of hypothalamic connectivity to the dorsal and ventral striatum in individual sleep homeostasis, suggesting that hypothalamus-dorsal striatum circuit may be a promising target for interventions mitigating excessive sleepiness and promoting alertness.

Theory-Based Determinants of Stopping Drowsy Driving Behavior in College Students: A Cross-Sectional Study.

Drowsy driving among college students is a critical public health issue due to its significant impact on road safety. This cross-sectional study aimed to investigate the determinants of stopping drowsy driving behavior among college students using the multi-theory model (MTM) of health behavior change. Data for this study were collected from September to October 2023 via a 42-item psychometric valid, web-based survey disseminated via Qualtrics, involving 725 students from a large southwestern university. Nearly half of the participants (49.38%) reported drowsy driving in the past month. Hierarchical multiple regression analysis revealed that participatory dialogue (p = 0.0008) and behavioral confidence (p < 0.0001) significantly predicted the initiation of refraining from drowsy driving, with the final model explaining 36.4% of the variance. Similarly, emotional transformation (p < 0.0001) and practice for change (p = 0.0202) significantly predicted the sustenance of behavior change, with the final model accounting for 40.6% of the variance. These findings underscore the importance of targeted MTM-based interventions focusing on enhancing students' awareness and confidence in managing drowsiness to mitigate drowsy driving, ultimately improving road safety and student well-being.

Feeling tired versus feeling relaxed: Two faces of low physiological arousal.

Human well-being and functioning depend on two fundamental mental states: Relaxation and sleepiness. Relaxation and sleepiness are both assumed to be states of low physiological arousal and negatively correlated. However, it is still unclear how consistent this negative relationship is across different settings and whether it changes before and after an intervention. Here we investigated this intricate relationship between subjective momentary sleepiness and relaxation states by meta-analytically analyzing several data sets from studies using the Relaxation State Questionnaire. We discovered that subjective sleepiness and relaxation were in fact anti-correlated pre-intervention. This anti-correlation provides a quantitative dissociation between sleepiness and relaxation. Thus, even though sleepiness and relaxation both implicate a low arousal level, the two mental states are subjectively experienced in a qualitatively different fashion, and thus reflect distinct underlying constructs. For the post-intervention relationship, this negative correlation could not be consistently found. This indicates that there are aspects of the experimental setting or intervention that introduce changes in the dynamics of the relationship of the two constructs.

How to quantify sleepiness during an attempt to sleep?

Background. Sleepiness assessment tools were mostly developed for detection of an elevated sleepiness level in the condition of sleep deprivation and several medical conditions. However, sleepiness occurs in various other conditions including the transition from wakefulness to sleep during an everyday attempt to get sleep.Objective. We examined whether objective sleepiness indexes can be implicated in detection of fluctuations in sleepiness level during the polysomnographically-monitored attempt to sleep, i.e. in the absence of self-reports on perceived sleepiness level throughout such an attempt.Approach. The polysomnographic signals were recorded in the afternoon throughout 106 90 min napping attempts of 53 university students (28 females). To calculate two objective sleepiness indexes, the electroencephalographic (EEG) spectra were averaged on 30 s epochs of each record, assigned to one of 5 sleep-wake stages, and scored using either the frequency weighting curve for sleepiness substate of wake state or loadings of each frequency on the 2nd principal component of variation in the EEG spectrum (either sleepiness score or PC2 score, respectively).Main results. We showed that statistically significant fluctuations in these two objective sleepiness indexes during epochs assigned to wake stage can be described in terms of the changes in verbally anchored levels of subjective sleepiness assessed by scoring on the 9-step Karolinska Sleepiness Scale.Significance. The results afford new opportunities to elaborate importance of intermediate substates between wake and sleep states for sleep-wake dynamics in healthy individuals and patients with disturbed sleep.

[The 509th case: fatigue, sleepiness, mood disorder, and hypothyroidism].

A 28-year-old woman presented with a 4-year history of fatigue and sleepiness and was found to have central hypothyroidism and mood disorder. The patient had normal thyroid volume and did not show any other pituitary axis involvement. Over the course of the disease, her symptom improvement matched with the free thyroxine (FT4) rebound and the adjustment of antipsychotic medication. The patient's grandmother had central hypothyroidism, and her mother and uncle had lowered or inappropriately normal thyroid stimulating hormone. Hence, genetic involvement was highly suspected, but whole exon sequencing did not reveal a pathogenic variant. Levothyroxine tablets were prescribed to maintain a normal median level of FT4, and mood disorder medications were adjusted by specialists. Isolated central hypothyroidism is extremely rare, and we report this case aiming to raise awareness of this condition.

Investigating the Link between Circadian Clock Gene Expressions, Chronotype, Insomnia, and Daytime Sleepiness in Patients with Obstructive Sleep Apnea.

INTRODUCTION: This study aimed to investigate the relationship between obstructive sleep apnea (OSA), circadian rhythms, and individual sleep-wake preferences, as measured by chronotype, and to assess the association between circadian clock gene expression and subjective sleep-related variables. METHODS: A total of 184 individuals were recruited, underwent polysomnography (PSG), and completed questionnaires including a chronotype questionnaire (CQ), insomnia severity index (ISI), and Epworth sleepiness scale (ESS). Blood samples were collected in the evening before and morning after PSG. Gene expression analysis included BMAL1, CLOCK, PER1, CRY1, NPAS2, and NR1D1. RESULTS: In the OSA group, the subjective amplitude (AM score of CQ) positively correlated with all circadian clock genes in the morning (R ≥ 0.230 and p < 0.05 for each one), while the morningness-eveningness (ME score of CQ) was only associated with the evening BMAL1 level (R = 0.192; p = 0.044). In healthy controls, insomnia severity correlated with evening expression of BMAL1, PER1, and CRY1. CONCLUSIONS: The findings highlight the complex interplay between OSA, circadian rhythms, and sleep-related variables, suggesting potential determinants of morning chronotype in OSA and implicating disrupted circadian clock function in subjective feelings of energy throughout the day. Further research is warranted to elucidate underlying mechanisms and guide personalized management strategies.

Ramadan fasting observance is associated with decreased sleep duration, increased daytime sleepiness and insomnia symptoms among student-athletes.

OBJECTIVE: To examine the relationships between Ramadan fasting observance (RFO) and sleep-wake patterns, daytime sleepiness, and insomnia levels in student-athletes. METHODS: Sleep was measured using wrist-actigraphy in 25 semi-professional student-athletes (mean ± SD; age = 22 ± 2 years, height = 182.0 ± 5.8 cm, body mass = 81.3 ± 15.2 kg) during seven nights before RFO (academic study period), during the first half of RFO (14 nights, holiday period), and the second half of RFO (14 nights, academic study period). Additionally, participants completed the Epworth Sleepiness Scale (ESS), Insomnia Severity Index (ISI) and Pittsburgh Sleep Quality Index (PSQI) questionnaires seven days before RFO and on the last day of RFO. RESULTS: Actigraphy results indicated RFO was associated with significant decreases in sleep duration during the second half of RFO vs. before and during the first half of RFO (p < 0.001). However, the first half of RFO was associated with a delay of ⁓ 2.5 h in sleep onset compared to before RFO; this delay persisted during the second half of RFO (p < 0.001). The total PSQI score before RFO (6.6 ± 2.3 AU) and during RFO (8.2 ± 2.3 AU) suggested poor overall sleep quality. ISI and ESS scores were greater during than before RFO (p = 0.002 and p = 0.041, respectively). CONCLUSIONS: The second half of RFO was associated with decreases in objectively assessed sleep duration among student-athletes. RFO was also associated with impaired sleep quality, excessive daytime sleepiness, and increased insomnia symptoms. Personalized interventions to address sleep-related issues in student-athletes during RFO are warranted.

Phenotyping patients treated for obstructive sleep apnea with persistent objective impaired alertness or subjective sleepiness.

BACKGROUND AND OBJECTIVES: Sleepiness in patients with obstructive sleep apnea (OSA) is associated with accidental and economic burden, as well as cardiovascular risk. Despite OSA treatment, 10-28 % of patients report residual sleepiness. Its determinants, as well as those of objective impaired alertness remain poorly known. In this study, we investigated factors associated with residual subjective sleepiness and objective impaired alertness in patients treated for OSA. METHODS: Consecutive OSA treated patients referred for maintenance of wakefulness tests (MWT) at a tertiary university center were recruited between 2017 and 2020. Clinical data and polysomnography parameters were compared between patients with vs without subjective sleepiness (Epworth Sleepiness Scale, ESS≥11) and those with vs without impaired alertness (at least one trial with sleep onset on MWT). A multivariate logistic model was used to assess explanatory variables of MWT and ESS results. RESULTS: We included 141 patients, of whom 12.8 % had both subjective sleepiness and objective impaired alertness, 17.7 % objective impaired alertness only and 9.2 % subjective sleepiness only. Self-reported history of car accident/near miss, smoking history and ESS≥11 were significantly associated with objective impaired alertness whereas residual Apnea-hypopnea Index and CPAP use were not. The only significant variable associated with ESS at the time of MWT evaluation was initial ESS. Patients with objective impaired alertness only were more often smokers (52 % vs 19 %, p = 0.01), had a higher body mass index (BMI) (32 vs 29 kg/m2, p = 0.05), and showed lower initial ESS (11 vs 13, p < 0.01). CONCLUSIONS: More than one third of OSA treated patients referred for MWT have objective impaired alertness and/or subjective sleepiness. Our findings highlight the need for a comprehensive medical assessment including accident history, subjective sleepiness and comorbidities. Particular attention should be paid to smoking patients with high BMI, who are at risk of impaired alertness with no report of subjective sleepiness.

Exploring sleepiness and stress among London bus drivers: An on-road observational study.

Bus driver sleepiness is commonplace but often goes unreported within the industry. Whilst past research has begun to shed a light on the prevalence, potential causes, and consequences of bus driver sleepiness, this is often done using self-report methods. This is the first study to investigate sleepiness amongst city bus drivers on-road using a live bus route with drivers' regular schedules. A total of 16 participants completed two drives of their regular bus route once during an early morning shift and once during a daytime shift whilst physiological and self-report measures of sleep and stress were taken. Prior to these drives, drivers recorded their sleep in a diary and wore an actigraph to obtain objective sleep measures. Results showed that most drivers did not obtain sufficient sleep prior to early morning shifts, and often did not obtain as much sleep as they would need in order to feel rested before work. Sleepiness and stress were observed in both shifts. During early morning shifts sleepiness was likely a result of working during circadian lows and not obtaining enough sleep prior to the shift. In contrast, sleepiness during the daytime shift was likely a result of completing a highly demanding task in complex traffic which not only contributed to fatigue, but also led to increased levels of stress. As well as demonstrating the prevalence of sleepiness amongst bus drivers, these findings show that the causes of sleepiness can be multifaceted and often come about due to a combination of work and personal factors. In addition, the experience of sleepiness is not the same for all drivers, with individual differences in the experience of sleepiness playing a large role. These differences highlight the need for individualised interventions which should be considered by policymakers alongside the combination of causal factors within a larger systems approach.

Occurrence of somnolence and respiratory depression induced by pregabalin and mirogabalin use and the influence of opioid treatment using the Japanese adverse drug event report database.

Background: Gabapentinoid anticonvulsants are standard treatment for neuropathic pain and are often combined with opioids for treating cancer. It is assumed that this combination may heighten somnolence and respiratory depression due to the inhibitory effects of opioids on the central nervous system. Although pregabalin, a gabapentinoid, is known to increase somnolence frequency during opioid therapy, whether mirogabalin exerts similar effects on somnolence frequency under opioid therapy remains unknown. This study examined the signals of somnolence and respiratory depression in response to pregabalin and mirogabalin use by utilizing data from the Japanese Adverse Drug Event Report database and assessed their interaction with strong opioid analgesics. Methods: Information was obtained from the JADER database from April 2004 to August 2023 via the Pharmaceuticals and Medical Devices Agency website. The study focused on neuropathic pain medications, specifically "pregabalin" and "mirogabalin besilate." Adverse events were defined using preferred terms (PTs) from the Medical Dictionary for Regulatory Activities version 26.1. The PTs considered were "Somnolence (10041349)" and "Respiratory depression (10038678)." To investigate the effect of the combination of strong opioid analgesics with pregabalin and mirogabalin on the occurrence of somnolence, a multivariable logistic regression analysis was conducted. Results: Signals for somnolence were detected with the use of both drugs (pregabalin: information component (IC) [95% confidence intervals (CIs)]: 2.89 [2.70 to 3.08]; mirogabalin: IC [95% CIs] 2.50 [1.85 to 3.16]). When evaluating respiratory depression, a typical and serious adverse event of opioid analgesic use, a signal was detected with pregabalin use but not with mirogabalin use (pregabalin: (IC [95% CIs] 1.28 [0.83 to 1.73]; mirogabalin: IC [95% CIs] -0.15 [-2.20 to 1.89]). Multivariable analysis indicated that the use of strong opioid analgesics increased the occurrence of somnolence when combined with pregabalin but not when combined with mirogabalin (p = 0.004). Conclusion: While the safety of concomitant administation of mirogabalin with opioids remains controversial, caution should be exercised when using pregabalin, especially in combination with opioids for neuropathic pain, compared to that for mirogabalin.

What the Fika? Implementation of Swedish Coffee Breaks During Emergency Medicine Conference.

Introduction: In this study we aimed to investigate the effects of incorporating Swedish-style fika (coffee) breaks into the didactic schedule of emergency medicine residents on their sleepiness levels during didactic sessions. Fika is a Swedish tradition that involves a deliberate decision to take a break during the workday and usually involves pastries and coffee. We used the Karolinska Sleepiness Scale to assess changes in sleepiness levels before and after the implementation of fika breaks. Methods: The study design involved a randomized crossover trial approach, with data collected from emergency medicine residents over a specific period. This approach was done to minimize confounding and to be statistically efficient. Results: Results revealed the average sleepiness scale was 4.6 and 5.5 on fika and control days, respectively (P = 0.004). Conclusion: Integration of fika breaks positively influenced sleepiness levels, thus potentially enhancing the educational experience during residency didactics.

Acute effects of a simulated quick return on subjective sleepiness, mood, and cognitive performance: A laboratory crossover controlled trial.

Sleep loss due to short time off between shifts has been proposed as a mechanism contributing to impaired functioning in occupational settings. This laboratory crossover trial (ClinicalTrials.gov identifier: NCT05162105, N = 66) compared subjective sleepiness, mood, and cognitive performance on a day shift after an evening shift with only 8 h off between shifts (quick return, QR) to a day shift after another day shift with 16 h off between shifts (control). Results indicated higher subjective sleepiness (Karolinska Sleepiness Scale) during the QR condition compared to the control condition (p < 0.001). No significant differences were found on mood (Positive and Negative Affect Schedule) and cognitive performance (Psychomotor Vigilance- and Digit Symbol Substitution Test) between the conditions. Findings of increased subjective sleepiness corroborate previous field studies. This trial is to our knowledge the first to compare mood and cognitive performance after a QR to a longer shift transition using an experimental design. Future research should explore the effects of accumulated sleep loss associated with QRs (e.g. having several QRs within a short time period) on behavioral outcomes.

Sleep quality and daytime sleepiness amongst family caregivers of children with Spinal Muscular Atrophy.

BACKGROUND: While there are limited studies focusing on sleep quality of family caregivers of children with Spinal Muscular Atrophy (SMA), there are no studies on daytime sleepiness in SMA. AIMS: This study aimed a) to compare the sleep quality and daytime sleepiness between caregivers of children with SMA and those of healthy peers and b) to investigate the sleep quality and daytime sleepiness of family caregivers of children with different types of SMA. METHODS AND PROCEDURES: This study included 30 family caregivers of children with SMA (SMA Type 1:12, SMA Type 2:10, and SMA Type 3:8) and 31 family caregivers of healthy peers. Sleep quality and daytime sleepiness of family caregivers were evaluated using the Pittsburg Sleep Quality Index (PSQI) and the Epworth Sleepiness Scale (EPS), consecutively. OUTCOMES AND RESULTS: Demographic characteristics of children with SMA and healthy peers were similar (p > 0.05). The mean ages of family caregivers of children with SMA and healthy peers were 36.07 ± 5.84 and 35.26 ± 5.02 years, respectively (p = 0.6). The PSQI scores of family caregivers of children with SMA (7.50 ± 3.90 points) were lower than those of healthy peers (4.09 ± 1.97 points) (p < 0.001). There was no difference in PSQI scores between SMA types (p = 0.8). Also, no difference was found between SMA types and between SMA and healthy peers in terms of EPS (p > 0.05). CONCLUSIONS AND IMPLICATIONS: Family caregivers of children with SMA had poor sleep quality but similar daytime sleepiness compared with those of healthy peers. Among SMA types, family caregivers had similar sleep quality and daytime sleepiness. It was demonstrated that the sleep quality of family caregivers should be taken into consideration in the disease management of SMA.

Daytime sleepiness in insomnia: Are we focusing on what truly matters?

Insomnia, the most prevalent sleep disorder, is commonly associated with other mental and somatic disorders, making it a significant health concern. It is characterized by nighttime symptoms and daytime dysfunction, with sleepiness being a potential criterion for the latter. Sleepiness is a normal physiological state that is typically experienced near usual bedtime, in normal circumstances. In insomnia, it seems somewhat logical the idea that there is significant daytime sleepiness. However, the topic has been the subject of various discussions in sleep medicine, with studies yielding contradictory and inconsistent results. In this article, we aim to critically examine daytime sleepiness in individuals with insomnia disorder and propose an alternative approach to addressing it, both in clinical practice and research settings. It is crucial to further investigate the role of daytime sleepiness in insomnia, particularly by focusing on sleepiness perception as a more relevant dimension to explore in majority of patients. It is plausible that certain insomnia phenotypes are objectively sleepy during the day, but more studies are necessary, particularly with well-defined clinical samples. The implications of assessing sleepiness perception in insomnia for clinical practice are discussed, and new avenues for research are suggested.

The effect of exercise on daytime sleepiness in healthy individuals.

The effects of exercise on daytime sleepiness remain unclear, with conflicting findings in the literature. We reviewed the existing literature on the relationship between exercise and daytime sleepiness in healthy individuals. We conducted a systematic search of PubMed and Google Scholar (1991 to present) for interventional studies that used the Epworth Sleepiness Scale (ESS) to measure change in self-reported degree of sleepiness before and after an exercise regimen. Seven studies were included in the review. Exercise significantly improved self-reported sleepiness after the intervention, as measured by ESS, in 4 of the 7 studies; the other studies indicated no significant difference. Additionally, exercise interventions enhanced sleep quality, evident in lower Pittsburgh Sleep Quality Index scores in 4 of 5 studies, thus indirectly alleviating daytime sleepiness. Results were variable and influenced by exercise type, intensity, and timing, as well as participant adherence. Factors that may contribute to the effect of exercise on daytime sleepiness include improved sleep quality, regulation of circadian rhythms, neurotransmitter release, stress reduction, increased energy levels, and weight reduction. This review suggests benefits of exercise for reducing daytime sleepiness and improving sleep quality. Future research is essential for assessing the mechanisms of these effects.

Driver drowsiness is associated with altered facial thermal patterns: Machine learning insights from a thermal imaging approach.

Driver drowsiness is a significant factor in road accidents. Thermal imaging has emerged as an effective tool for detecting drowsiness by enabling the analysis of facial thermal patterns. However, it is not clear which facial areas are most affected and correlate most strongly with drowsiness. This study examines the variations and importance of various facial areas and proposes an approach for detecting driver drowsiness. Twenty participants underwent tests in a driving simulator, and temperature changes in various facial regions were measured. The random forest method was employed to evaluate the importance of each facial region. The results revealed that temperature changes in the nasal area exhibited the highest value, while the eyes had the most correlated changes with drowsiness. Furthermore, drowsiness was classified with an accuracy of 88 % utilizing thermal variations in the facial region identified as the most important regions by the random forest feature importance model. These findings provide a comprehensive overview of facial thermal imaging for detecting driver drowsiness and introduce eye temperature as a novel and effective measure for investigating cognitive activities.

Considerations towards a neurobiologically-informed EEG measurement of sleepiness.

Sleep is a daily experience across humans and other species, yet our understanding of how and why we sleep is presently incomplete. This is particularly prevalent in research examining the neurophysiological measurement of sleepiness in humans, where several electroencephalogram (EEG) phenomena have been linked with prolonged wakefulness. This leaves researchers without a solid basis for the measurement of homeostatic sleep need and complicates our understanding of the nature of sleep. Recent theoretical and technical advances may allow for a greater understanding of the neurobiological basis of homeostatic sleep need: this may result from increases in neuronal excitability and shifts in excitation/inhibition balance in neuronal circuits and can potentially be directly measured via the aperiodic component of the EEG. Here, we review the literature on EEG-derived markers of sleepiness in humans and argue that changes in these electrophysiological markers may actually result from neuronal activity represented by changes in aperiodic markers. We argue for the use of aperiodic markers derived from the EEG in predicting sleepiness and suggest areas for future research based on these.

Quick returns, sleep, sleepiness and stress - An intra-individual field study on objective sleep and diary data.

OBJECTIVES: Quick returns (<11 hours of rest between shifts) have been associated with shortened sleep length and increased sleepiness, but previous efforts have failed to find effects on sleep quality or stress. A shortcoming of most previous research has been the reliance on subjective measures of sleep. The aim of this study was to combine diary and actigraphy data to investigate intra-individual differences in sleep length, sleep quality, sleepiness, and stress during quick returns compared to day-day transitions. METHODS: Of 225 nurses and assistant nurses who wore actigraphy wristbands and kept a diary of work and sleep for seven days, a subsample of 90 individuals with one observation of both a quick return and a control condition (day-day transition) was extracted. Sleep quality was assessed with actigraphy data on sleep fragmentation and subjective ratings of perceived sleep quality. Stress and sleepiness levels were rated every third hour throughout the day. Shifts were identified from self-reported working hours. Data was analyzed in multilevel models. RESULTS: Quick returns were associated with 1 hour shorter sleep length [95% confidence interval (CI) -1.23- -0.81], reduced subjective sleep quality (-0.49, 95% CI -0.69- -0.31), increased anxiety at bedtime (-0.38, 95% CI -0.69- -0.08) and increased worktime sleepiness (0.45, 95%CI 0.22- 0.71), compared to day-day transitions. Sleep fragmentation and stress ratings did not differ between conditions. CONCLUSIONS: The findings of impaired sleep and increased sleepiness highlight the need for caution when scheduling shift combinations with quick returns.

Worse sleep architecture but not self-reported insomnia and sleepiness is associated with higher cortisol levels in menopausal women.

OBJECTIVE: Worsening of sleep quality during menopause is well recognized. However, the underlying hormonal regulation is insufficiently described. In this study, we evaluated associations between sleep and cortisol levels. STUDY DESIGN: Seventeen perimenopausal and 18 postmenopausal women were enrolled in a three-night sleep study. Diurnal blood sampling was performed during the third night and the following day. MAIN OUTCOME MEASURES: Self-reported insomnia and sleepiness were evaluated with the Basic Nordic Sleep Questionnaire and sleep architecture with all-night polysomnography. Diurnal cortisol samples were collected at 20-min intervals. Correlation analyses and generalized linear models adjusted by age, body mass index, vasomotor symptoms and depressive symptoms were conducted. RESULTS: In correlation analyses, self-reported insomnia and sleepiness were not associated with cortisol levels. Lower sleep efficiency, slow-wave sleep and stage 1 percentages, number of slow-wave sleep and of rapid-eye-movement (REM) periods, longer slow-wave sleep latency and higher wake after sleep onset percentage were associated with higher cortisol levels (all p < 0.05). Further, lower slow-wave sleep percentage and longer slow-wave sleep latency correlated with steeper daytime cortisol slope (i.e. day cortisol decrease, both p < 0.05). In adjusted generalized linear models, lower sleep efficiency and number of rapid-eye-movement periods as well as higher wake after sleep onset percentage correlated with higher cortisol levels; lower slow-wave sleep percentage correlated with higher cortisol awakening response. CONCLUSIONS: Worse sleep architecture but not worse self-reported insomnia and sleepiness was associated with higher cortisol levels. This is important for understanding sleep in women, especially during the menopausal period.