Estimating daytime sleepiness with previous night electroencephalography,electrooculography, and electromyography spectrograms in patients with suspected sleep apnea using a convolutional neural network

A common symptom of obstructive sleep apnea (OSA) is excessive daytime sleepiness (EDS). The gold standard test for EDS is the multiple sleep latency test (MSLT). However, due to its high cost, MSLT is not routinely conducted for OSA patients and EDS is instead evaluated using sleep questionnaires. This is problematic however, since sleep questionnaires are subjective and correlate poorly with the MSLT. Therefore, new objective tools are needed for reliable evaluation of EDS. The aim of this study was to test our hypothesis that EDS can be estimated with neural network analysis of previous night polysomnographic signals. We trained a convolutional neural network (CNN) classifier using electroencephalography, electrooculography, and chin electromyography signals from 2,014 patients with suspected OSA. The CNN was trained to classify the patients into four sleepiness categories based on their mean sleep latency (MSL); severe (MSL < 5min), moderate (5 ≤ MSL < 10), mild (10 ≤ MSL < 15), and normal (MSL ≥ 15). The CNN classified patients to the four sleepiness categories with an overall accuracy of 60.6% and Cohen’s kappa value of 0.464. In two-group classification scheme with sleepy (MSL < 10 min) and non-sleepy (MSL ≥ 10) patients, the CNN achieved an accuracy of 77.2%, with sensitivity of 76.5%, and specificity of 77.9%. Our results show that previous night’s polysomnographic signals can be used for objective estimation of EDS with at least moderate accuracy. Since the diagnosis of OSA is currently confirmed by polysomnography, the classifier could be used simultaneously to get an objective estimate of the daytime sleepiness with minimal extra workload.     

Warm ears,a red flag for sleepiness?

Core body and skin temperatures are intimately linked to sleep and alertness. The distal-to-proximal skin temperature gradient has been described as a good physiological predictor for sleep onset. Increased ear skin temperature is often caused by increased blood flow reflected in redness, which is commonly noticed in people who are sleepy, especially anecdotally in children. Nonetheless, no prior study investigated the possible relation between sleepiness and ear skin temperature as a separate measurement. We assessed the relation between ear skin temperature and sleepiness in patients undergoing regular electroencephalographic examinations, because of suspicion of epilepsy, both without and after sleep deprivation. Subjective sleepiness was measured using the Stanford Sleepiness Scale, and objective sleepiness by determining sleep onset with electroencephalography. Distal, proximal and ear skin temperature were measured repeatedly using wireless measurement devices (iButtons). Forty-four adult patients were included. Ear skin temperature correlates weakly with distal skin temperature (r = 0.174, p < 0.001) and distal-to-proximal gradient (r = 0.160, p < 0.001), but not with proximal skin temperature (r = −0.001, p = 0.975). Ear skin temperature increased significantly in a subgroup of 13 patients, between 5 and 1 min before sleep onset (p = 0.002; η² = 0.059), even though this increase was also associated with supine posture. iButtons is a valid method to measure ear skin temperature, which appears to function partly like a distal and partly like a proximal skin temperature measurement. Change in ear skin temperature is associated with sleep onset and supine posture.     

Objective measure of sleepiness and sleep latency via bispectrum analysis of EEG

Chronic sleepiness is a common symptom in the sleep disorders, such as, Obstructive Sleep Apnea, Periodic leg movement disorder, narcolepsy, etc. It affects 8% of the adult population and is associated with significant morbidity and increased risk to individual and society. MSLT and MWT are the existing tests for measuring sleepiness. Sleep Latency (SL) is the main measures of sleepiness computed in these tests. These are the laboratory-based tests and require services of an expert sleep technician. There are no tests available to detect inadvertent sleep onset in real time and which can be performed in any professional work environment to measure sleepiness level. In this article, we propose a fully automated, objective sleepiness analysis technique based on the single channel of EEG. The method uses a one-dimensional slice of the EEG Bispectrum representing a nonlinear transformation of the underlying EEG generator to compute a novel index called Sleepiness Index. The SL is then computed from the SI. Working on the patient’s database of 42 subjects we computed SI and estimated SL. A strong significant correlation (r ≥ 0.70, s < 0.001) was found between technician scored SL and that computed via SI. The proposed technology holds promise in the automation of the MSLT and MWT tests. It can also be developed into a sleep management system, wherein the SI is incorporated into a sleepiness index alert unit to alarm the user when sleepiness level crosses the predetermined threshold.     

Post‐CPAP sleepiness – a specific syndrome?

Following treatment with continuous positive airway pressure (CPAP), some patients with obstructive sleep apnoea (OSA) remain sleepy despite effective CPAP and attention to other diagnoses that can provoke sleepiness. It is unclear if this residual sleepiness is an irreversible result of their previous OSA and merits consideration for pharmacological treatment or simply because of the many and varied causes of sleepiness normally found in the community. We have measured levels of sleepiness, using the Epworth Sleepiness Score (ESS), in 572 patients on CPAP and compared them with a control group of 525 subjects from a community survey, which would have included the usual lifestyle reasons for sleepiness as well as any undiagnosed sleep disorders. There was no difference in the percentage of patients with an ESS >10 in the CPAP group compared with the controls (16.1 versus 14.3, P = 0.54). Thus, although there clearly are sleepy patients within the CPAP group, the prevalence is no higher than in the community. We question whether so-called 'post-CPAP sleepiness' should be regarded as any more abnormal and worthy of treatment than a 'normal' population. Post-CPAP sleepiness as a specific disorder may not exist.     

Maintenance of Wakefulness Test scores and driving performance in sleep disorder patients and controls

Objective

Sleepiness at the wheel is a risk factor for traffic accidents. Past studies have demonstrated the validity of the Maintenance of Wakefulness Test (MWT) scores as a predictor of driving impairment in untreated patients with obstructive sleep apnea syndrome (OSAS), but there is limited information on the validity of the maintenance of wakefulness test by MWT in predicting driving impairment in patients with hypersomnias of central origin (narcolepsy or idiopathic hypersomnia). The aim of this study was to compare the MWT scores with driving performance in sleep disorder patients and controls.

Methods

19 patients suffering from hypersomnias of central origin (9 narcoleptics and 10 idiopathic hypersomnia), 17 OSAS patients and 14 healthy controls performed a MWT (4 × 40-minute trials) and a 40-minute driving session on a real car driving simulator. Participants were divided into 4 groups defined by their MWT sleep latency scores. The groups were pathological (sleep latency 0–19 min), intermediate (20–33 min), alert (34–40 min) and control (> 34 min). The main driving performance outcome was the number of inappropriate line crossings (ILCs) during the 40 minute drive test.

Results

Patients with pathological MWT sleep latency scores (0–19 min) displayed statistically significantly more ILC than patients from the intermediate, alert and control groups (F (3, 46) = 7.47, p < 0.001).

Interpretation

Pathological sleep latencies on the MWT predicted driving impairment in patients suffering from hypersomnias of central origin as well as in OSAS patients. MWT is an objective measure of daytime sleepiness that appears to be useful in estimating the driving performance in sleepy patients.     

Exenatide improves excessive daytime sleepiness and wakefulness in obese patients with type 2 diabetes without obstructive sleep apnoea

We investigate the effects of exenatide on excessive daytime sleepiness (EDS), driving performance and depression score in patients with type 2 diabetes with EDS. Eight obese patients with diabetes but without obstructive sleep apnoea (OSA) participated in a placebo‐controlled single‐blind study during which multiple wakefulness and sleep latency test, Epworth score, driving performance, depression score, fasting glucose and glycated haemoglobin (HbA1c) levels were assessed at baseline, end of placebo and treatment phase at baseline and after 22 weeks of treatment. Mean (±standard error of the mean) age, body mass index (kg m²) and HbA1c [mmol mol^?1 (%)] of patients at baseline were 50 ± 4.9 years, 37.6 ± 1.1 and 65 ± 19 (8.06 ± 0.41), respectively. When compared to placebo, exenatide treatment was associated with a decrease in both subjective and objective sleepiness, based on the Epworth score reduction and the sleep latency increase assessed by multiple objective sleepiness and sustained attention (OSLER) tests, respectively. Mean sleep latency time (adjusted for change in HbA1c and weight) were 32.1 ± 1.7, 29.1 ± 1.7 and 37.7 ± 1.7, respectively (P = 0.002). Modelling for covariates suggested that improvement in mean sleep latency time is predicted by changes in weight (P = 0.003), but not by changes in HbA1c (P = 0.054). Epworth sleepiness score was reduced significantly (values for placebo versus exenatide: 11.3 ± 1.2 versus 5.7 ± 1.3; P = 0.003). No significant change was noted in the depression score and driving performance. Exenatide is associated with a significant reduction in objective sleepiness in obese patients with type 2 diabetes without OSA, independent of HbA1c levels. These findings could form a basis for further studies to investigate the pathophysiological mechanisms of sleepiness in obese patients with type 2 diabetes.     

Maintenance of wakefulness test as a predictor of driving performance in patients with untreated obstructive sleep apnea

STUDY OBJECTIVE: To determine the ability of Maintenance of Wakefulness Test (MWT) to predict simulated driving performance in patients suffering from sleep apnea syndrome. DESIGN: Study involving one hour of simulated driving, one night of polysomnography (PSG), and a 4 x 40-minute MWT. SETTING: Sleep laboratory. PATIENTS: Thirty male patients with untreated obstructive sleep apnea syndrome (OSAS) (mean age [+/- SD] = 51 +/- 8 years, range 34-62; mean body mass index (BMI) [+/- SD] = 29 +/- 3, range 24-37; mean apnea/hypopnea index (AHI) [+/- SD] = 43 +/- 24, range 14-96). As defined by MWT mean sleep latency, 23.3% of the patients were sleepy (0-19 min), 33.3% were alert (20-33 min), and 43.4% were fully alert (34-40 min). MEASUREMENTS: Nocturnal PSG, mean sleep latency at 4 x 40-minute MWT trials, Epworth Sleepiness Scale (ESS), and standard deviation from the center of the road (SDS) on driving simulator. RESULTS: Mean MWT scores inversely correlated with SDS during the simulated driving session (Pearson's r = -0.513, P < 0.01). We found a significant effect of MWT groups (sleepy, alert, or fully alert) on SDS (ANOVA, F(2, 29) = 5.861, P < 0.01). Post hoc tests revealed that the sleepy group had a higher SDS than the fully alert group (P = 0.006). ESS, AHI, microarousal index, and total sleep time did not predict simulated driving performance. CONCLUSIONS: A pathological MWT mean sleep latency (0-19 min) is associated with simulated driving impairment. Before MWT can be used to predict the driving ability of untreated patients with OSAS, further studies are needed to confirm that pathological MWT scores are associated with real driving impairment.     

Definition of excessive daytime sleepiness in the general population: Feeling sleepy relates better to sleep‐related symptoms and quality of life than the Epworth Sleepiness Scale score. Results from an epidemiological study

Many different subjective tools are being used to measure excessive daytime sleepiness (EDS) but the most widely used is the Epworth Sleepiness Scale (ESS). However, it is unclear if using the ESS is adequate on its own when assessing EDS. The aim of this study was to estimate the characteristics and prevalence of EDS using the ESS and the Basic Nordic Sleep Questionnaire (BNSQ) in general population samples. Participants aged 40 years and older answered questions about sleepiness, health, sleep‐related symptoms and quality of life. Two groups were defined as suffering from EDS: those who scored >10 on the ESS (with increased risk of dozing off) and those reporting feeling sleepy during the day ≥3 times per week on the BNSQ. In total, 1,338 subjects (53% male, 74.1% response rate) participated, 13.1% reported an increased risk of dozing off, 23.2% reported feeling sleepy and 6.4% reported both. The prevalence of restless leg syndrome, nocturnal gastroesophageal reflux, difficulties initiating and maintaining sleep and nocturnal sweating was higher among subjects reporting feeling sleepy compared to non‐sleepy subjects. Also, subjects reporting feeling sleepy had poorer quality of life and reported more often feeling unrested during the day than non‐sleepy subjects. However, subjects reporting increased risk of dozing off (ESS > 10) without feeling sleepy had a similar symptom profile as the non‐sleepy subjects. Therefore, reporting only risk of dozing off without feeling sleepy may not reflect problematic sleepiness and more instruments in addition to ESS are needed when evaluating daytime sleepiness.     

Determinants of depressive mood in coronary artery disease patients with obstructive sleep apnea and response to continuous positive airway pressure treatment in non‐sleepy and sleepy phenotypes in the RICCADSA cohort

We explored determinants of depressive mood in adults with coronary artery disease and obstructive sleep apnea and response to positive airway pressure treatment in sleepy and non‐sleepy phenotypes. In this secondary analysis of the RICCADSA trial conducted in Sweden, 493 cardiac patients with obstructive sleep apnea (n = 386) or no obstructive sleep apnea (n = 107) with complete Epworth Sleepiness Scale and Zung Self‐rating Depression Scale questionnaires were included. Sleepy (Epworth Sleepiness Scale ≥10) versus non‐sleepy (Epworth Sleepiness Scale <10) patients with depressive mood (Zung Self‐rating Depression Scale score ≥50) were evaluated after 3 and 12 months of positive airway pressure treatment. In all, 133 patients (27.0%) had depressive mood (29.3% of obstructive sleep apnea versus 18.7% of no obstructive sleep apnea; p = 0.029), with a higher percentage among the sleepy phenotype (36.9% versus 24.5%; p = 0.009). In multivariate analysis, depressive mood was significantly associated with female sex, body mass index and Epworth Sleepiness Scale. Among 97 obstructive sleep apnea patients with depressive mood at baseline, there was a significant reduction in the scores at follow‐up both in the sleepy and non‐sleepy patients allocated to positive airway pressure treatment, whereas no significant changes were observed in the untreated group (p = 0.033). The device use (hr/night) predicted improvement in mood (odds ratio, 1.33; 95% confidence interval, 1.10–1.61; p = 0.003) adjusted for age, female sex, body mass index, left ventricular ejection fraction, apnea–hypopnea index and delta Epworth Sleepiness Scale score. We conclude that obstructive sleep apnea was associated with depressive mood in adults with coronary artery disease. Treatment with positive airway pressure improved mood in both phenotypes, independent of the confounding factors.     

Sleepiness and residual sleepiness in adults with obstructive sleep apnea

Sleepiness is a common, but not necessary symptom of the obstructive sleep apnea syndrome (OSA) and is a frequent chief complaint of patients with OSA who seek medical attention. While sleepiness may seem simple in nature, the underlying mechanisms producing daytime sleepiness in OSA are complex and poorly characterized. Moreover, the meaningful assessment of pathological sleepiness is frequently far from straightforward. Effective treatment of OSA is generally expected to resolve or ameliorate daytime sleepiness. An unknown percentage of treated OSA patients, however, remain sleepy during waking hours. The assessment and treatment of residual sleepiness in treated OSA can range from simple to difficult, depending on the nature and causes of the continued sleepiness. Recently, however, data from clinical trials have been generated which provide direction in the evaluation and management of the OSA patient suffering residual daytime sleepiness.     

A behavioural test to assess daytime sleepiness in obstructive sleep apnoea

Daytime sleepiness is an important symptom of obstructive sleep apnoea syndrome (OSAS). The standard tests for its objective quantification use EEG recordings, and are time consuming and expensive, which makes them difficult to use for large studies. This study assesses the ability of a simple test of sustained ‘wakefulness’ to discriminate the excessive somnolence of severe symptomatic obstructive sleep apnoea from normality, and compares its results to the traditional EEG based Maintenance of Wakefulness Test (MWT). Ten subjects (7M 3F) with severe sleep apnoea (>4% SaO₂ dip rate median 32.7 (90% central range 9.7–65.6)) and symptoms of daytime sleepiness, (Epworth Sleepiness Score (ESS)17(10–24)) and 10 normal subjects (4M 6F, ESS 3.5(1–8)) were studied. The MWT and the behavioural test (Oxford SLEep Resistance test – OSLER test) were performed on each subject in random order on 2 separate days. The protocol for both tests was the same with 4 × 40 min sleep resistance challenges throughout the day while sound isolated in a darkened room. During the OSLER test subjects were asked to press a switch in response to a light emitting diode (LED), which was lit for 1 s in every three. Both the switch and the light were connected to a computer that stored both the number of times the light was illuminated and whether a correct response was made. The OSLER test discriminated the normal subjects from the sleep apnoea group (mean sleep latency (min) normal group 39.8, OSA group 10.5) as well as the traditional MWT (normal group 38.1, OSA group 7.3) and was much simpler to administer. This test has the advantage that sleep onset is defined objectively and automatically as a failure to respond to the light, rather than from EEG interpretation, which is inevitably partly subjective. This technique may provide a simple and robust method of objectively quantifying daytime sleepiness for large studies.     

Daytime Sleepiness and Driving Performance in Patients with Obstructive Sleep Apnea: Comparison of the MSLT,the MWT,and a Simulated Driving Task

Study Objectives:

To test the reliability of a driving-simulation test for the objective measurement of daytime alertness compared with the Multiple Sleep Latency Test (MSLT) and with the Maintenance of Wakefulness Test (MWT), and to test the ability to drive safely, in comparison with on-road history, in the clinical setting of untreated severe obstructive sleep apnea.

Design:

N/A.

Setting:

Sleep laboratory.

Patients or Participants:

Twenty-four patients with severe obstructive sleep apnea and reported daytime sleepiness varying in severity (as measured by the Epworth Sleepiness Scale).

Interventions:

N/A.

Measurements and Results:

Patients underwent MSLT and MWT coupled with 4 sessions of driving-simulation test on 2 different days randomly distributed 1 week apart. Simulated-driving performance (in terms of lane-position variability and crash occurrence) was correlated with sleep latency on the MSLT and more significantly on the MWT, showing a predictive validity toward the detection of sleepy versus alert patients with obstructive sleep apnea. In addition, patients reporting excessive daytime sleepiness or a history of car crashes showed poorer performances on the driving simulator.

Conclusions:

A simulated driving test is a suitable tool for objective measurement of daytime alertness in patients with obstructive sleep apnea. Further studies are needed to clarify the association between simulated-driving performance and on-road crash risk of patients with sleep disordered breathing.

Citation:

Pizza F; Contardi S; Mondini S; Trentin L; Cirignotta F. Daytime sleepiness and driving performance in patients with obstructive sleep apnea: comparison of the MSLT, the MWT, and a simulated driving task. SLEEP 2009;32(3):382-391.     

Young drivers who continue to drive while sleepy: What are the associated sleep‐ and driving‐related factors?

Crashes due to sleepiness account for a substantial proportion of road crash incidents. The purpose of the current study was to examine several sleep‐related factors and driving‐related factors for their association with self‐reports of continuing to drive while sleepy. In total 257 young drivers aged 18–25 years completed an online survey that assessed factors such as sleep quality, sleep duration and consistency, excessive daytime sleepiness, experiences with sleepiness and their driving‐related behaviours. The results demonstrate that being older, having a perceived ability to overcome sleepiness, committing more highway code violations and having experienced a sleep‐related close call were positively associated with an increased likelihood of continuing to drive while sleepy. The obtained results highlight the acceptance of risky driving behaviours among some younger drivers. Younger drivers’ risky driving behaviour is certainly a road safety concern given the impairment associated with sleepiness and their over‐representation in road crash incidents.     

The prevalence of excessive sleepiness is higher in shift workers than in patients with obstructive sleep apnea

Excessive daytime sleepiness (EDS) is a common feature among shift workers as well as in obstructive sleep apnea (OSA) patients. There are several important accidents related to sleep disturbances causing EDS. The aim of this study was to evaluate EDS in a group of shift workers (regular rotating) from civil aviation and to compare them with OSA patients (n = 300) and with a group of regular workers (RW) (n = 140). Our sample was composed of 730 working‐age individuals (aged 18–67 years). The regular rotating shift workers (SW) sample was composed of 290 aeronautical mechanics. EDS was evaluated with the Epworth Sleepiness Scale (ESS) and defined as a score ≥ 11. The prevalence value obtained for the EDS of RW was 37.1%, for SW it was 60.7% and for OSA patients it was 40.7%. A logistic regression model for EDS in a subsample composed of men and matched for age and BMI, controlling for self‐reported sleep duration, showed an increased risk of EDS for SW (OR = 3.91, p = .001), with the RW group as reference. OSA patients did not differ from RW on EDS levels. This study emphasizes the presence of EDS in a shift work group of civil aviation professionals, which exceeded the EDS level of a positive control group of OSA patients. Sleep hygiene education for companies' workers and management is important and mitigation strategies should be implemented to reduce excessive sleepiness among workers.     

Comparison of the maintenance of wakefulness test (MWT) to a modified behavioral test (OSLER) in the evaluation of daytime sleepiness

The objectives were to evaluate the correlation between sleep onset as defined by the Oxford sleep resistance (OSLER) test and by simultaneous electroencephalography (EEG) and to determine the correlation between sleep latencies measured by the OSLER test and maintenance of wakefulness test (MWT) performed on the same day. This was a prospective, cross-sectional study carried out in a tertiary-care university-based sleep laboratory. Participants were 11 consecutive subjects presenting to the sleep center with clinical indications for nocturnal polysomnography and MWT. The interventions included MWT and OSLER test. Mean sleep latencies for the OSLER and MWT in each subject were closely correlated (ICC = 0.94, [Intra-class correlation]P < 0.05). Sleep latency by OSLER and simultaneous measurement of EEG also had excellent agreement (ICC = 0.91) with a bias of -0.97 min. The OSLER test is a practical and reliable tool for evaluating daytime sleepiness when compared with the MWT. No obvious systematic adaptation was seen during sequential OSLER test performance. Given its portability and minimal technical requirements, the OSLER test may be useful for large-scale applications in the evaluation of daytime wakefulness and vigilance.     

The clinical value of the maintenance of wakefulness test (MWT) in the differentiation of children with attention deficit hyperactivity disorder (ADHD) and disorders of excessive somnolence

Summary Introduction   Attention deficit hyperactivity disorder is one of the most common child and adolescent psychiatric disorders. Probably a dysfunctional arousal regulation may play an important role in its pathogenesis. According to this hypothesis ADHD children may present an hypoarousal state with impaired daytime vigilance when confrontated with monotonous, repetetive tasks. Methods   We assessed the daytime wakefulness of 23 ADHD children and 6 children with excessive somnolence (narcolepsy, idiopathic CNS hypersomnia) using the Maintenance of Wakefulness Test (MWT) as a measure to determine objectively a subjects' ability to stay awake under soporific conditions. Results   Results indicate that there is no impaired daytime wakefulness in ADHD children, whether their nighttime sleep was disturbed or not. Mean sleep latencies across all MWT trials were similar for both groups groups (17.2 min. vs 16.3 min). In contrast children with an increased daytime sleepiness presented a shortened mean sleep latency during the trials (8.9 min). Aditionally more children of this group fell asleep during MWT compared to ADHD children (72 % vs 40.6 %). Conclusion   We speculate that due to the occurrence of attention problems in both disorders, the MWT might become a feasable, objective instrument in clinical practice for differential diagnostic.     

Effects of the presence of hypertension on the relationship between obstructive sleep apnoea and sleepiness

Obstructive sleep apnoea (OSA) plays a significant role in increasing blood pressure. Significant decreases were reported in blood pressure of hypertensive OSA patients with sleepiness who underwent continuous positive airway pressure (CPAP) treatment, but not in non-sleepy hypertensive OSA patients. More recently, however, significant decreases in blood pressure in non-sleepy hypertensive OSA patients following CPAP were shown. Effects of sleepiness on hypertension in OSA patients have been investigated, but not the effects of hypertension on sleepiness in OSA patients. We investigated the relationships between hypertension and sleepiness in patients with OSA. We analysed data on 275 middle-aged male subjects from a cross-sectional epidemiological health survey. We measured blood pressure and sleep duration objectively using an actigraph for 7 days and the respiratory disturbance index (RDI) with a type 3 portable device for 2 nights, and assessed sleepiness using the Epworth Sleepiness Scale (ESS). The RDI correlated significantly with ESS scores in the 88 hypertensive subjects (r = 0.33, P = 0.0024), but not in the 187 non-hypertensive subjects (r = -0.01, P = 0.91). Short sleep duration correlated significantly with ESS scores in both groups. Both the RDI and short sleep duration were related independently to sleepiness in only hypertensive subjects. Furthermore, the RDI was related negatively significantly to sleep duration in hypertensive subjects. Although short sleep duration was related significantly to sleepiness in both groups, hypertension may be important for the sleepiness in OSA patients. Detailed mechanisms of the difference in the relationship between sleepiness and the severity of OSA with or without hypertension should be studied further.     

Shine light on sleep: Morning bright light improves nocturnal sleep and next morning alertness among college students

The relationship between daytime light, especially morning light and sleep, has not been well documented. People who work in an office spend most of their time indoors and thus have less access to high-level daylight. The current study employed a field intervention approach to investigate whether exposure to 1.5 h of bright electric light in the early morning for 1 workweek would benefit sleep among students who spent most of their time in an office at the university. Twelve students (24.92 ± 1.78 years) underwent a 2 workday baseline measurement and two inconsecutive 5 workday interventions (with 1 week washout) with morning bright light and regular office light (1000 lx, 6500 K vs. 300 lx, 4000 K, at eye level). The sleep outcomes were recorded with actigraphy and a sleep diary. In addition, self-ratings of daytime sleepiness, mood, mental fatigue, perceived effort, and next morning sleepiness were measured each workday. The results showed that exposure to morning bright light versus regular office light yielded a higher sleep efficiency (83.82% ± 1.60 vs. 80.35% ± 1.57, p = 0.02), a smaller fragmentation index (15.26% ± 1.31 vs. 17.18% ± 1.28, p = 0.05), and a shorter time in bed (7.12 ± 0.13 vs. 7.51 ± 0.12, p = 0.03). Meanwhile, an earlier sleep onset time, shorter sleep latency, and lower morning sleepiness were observed after a 5 workday morning bright light intervention compared with the baseline (ps <0.05), no such benefit was found for self-ratings (ps >0.05). These findings support existing evidence that morning bright light could function as an enhancer of sleep and alertness for office occupants.     

Excessive daytime sleepiness in patients suffering from different levels of obstructive sleep apnoea syndrome

Excessive daytime sleepiness (EDS) is a frequent symptom of patients with obstructive sleep apnoea (OSA). EDS is a high-risk factor for accidents at work and on the road. Thirty untreated patients with different levels of severity of OSA were studied concerning night sleep and EDS. The criterion for severity was the respiratory disturbance index (RDI): 15 patients were classified as 'moderately' apnoeic (RDI < 40), 15 as 'severely' apnoeic (RDI > 40). Following night-time polysomnography, objective and subjective aspects of EDS were studied. To assess objective EDS the Maintenance of Wakefulness Test (MWT) and a computer-based vigilance performance test were used. Subjective EDS was determined using the Stanford Sleepiness Scale (SSS), the Epworth Sleepiness Scale (ESS) and the Visual Analogue Scales for Performance (VAS-P) and Tiredness (VAS-T). Well-being was assessed using the Scale of Well-Being by von Zerssen (Bf-S/Bf-S'). Severe apnoea patients spent more time in stage 1 and less in slow-wave sleep. MWT latencies tended to be shorter in the severe apnoea group. Vigilance testing revealed no group differences. Patients with moderate apnoea described themselves as more impaired in all subjective scales, but only SSS scores reached statistical significance. Our results suggest that there is no simple correlation between polysomnographic and respiratory sleep variables at night on the one hand, and the extent of EDS on the other hand. Furthermore, subjective and objective evaluation of EDS does not yield the same results. New approaches which allow a more detailed analysis of night sleep and daytime function are required to identify high-risked patients.     

Microarousals in patients with sleep apnoea/hypopnoea syndrome

SUMMARY Upper airway obstructions during sleep cause recurrent brief awakenings or microarousals. Standard criteria exist for sleep and respiratory event scoring, however, there are different definitions currently used to score microarousals. We therefore compared three definitions of microarousal (ranging from 1.5-3 s in duration) and one of awakening (> 15 s). We examined their occurrence at the termination of apnoeas and hypopnoeas and their correlation with daytime sleepiness in patients with sleep apnoea/hypopnoea syndrome (SAHS). Sixty-three patients (aged 49, SD 10) had overnight polysomnography, multiple sleep latency tests (MSLT) and Epworth Sleepiness Scales (ESS). There were significantly more microarousals by any definition than there were awakenings (P<0.001) and there were more 1.5 s than 3 s microarousals (P<0.001). Significantly more apnoeas and hypopnoeas were terminated by 1.5 s microarousals (83% and 81%) than by 3 s microarousals (75%) (all P<0.001). Apnoea/hypopnoea index (AHI) correlated significantly with objective daytime sleepiness (p = -0.30, P<0.01). There were weakly significant relationships between all three microarousal definitions (-0.24<P< -0.22, 0.03<P<0.04) and objective daytime sleepiness. None of the arousal definitions correlated with Epworth Sleepiness Scales scores. These results suggest that although 1.5 s microarousals are found at the end of more respiratory events, relationships between 3 and 1.5 s definitions, and daytime sleepiness are similar. This indicates that any of the three microarousal definitions can be used for visual assessment of sleep fragmentation.