Efficacy of Maxillomandibular Advancement Examined with Drug-Induced Sleep Endoscopy and Computational Fluid Dynamics Airflow Modeling.

OBJECTIVES: To use drug-induced sedation endoscopy (DISE) and computational fluid dynamics (CFD) modeling to study dynamic airway and airflow changes after maxillomandibular advancement (MMA), and how the changes correlate with surgical success based on polysomnography parameters. STUDY DESIGN: Retrospective cohort study. SETTING: University medical center. METHODS: DISE was rated with the VOTE (velum, oropharynx, tongue, epiglottis) classification, and CFD was used to model airflow velocity and negative pressure exerted on pharyngeal wall. Changes in VOTE score by site and CFD measurements were correlated with perioperative polysomnography outcomes of apnea-hypopnea index (AHI), apnea index (AI), oxygenation desaturation index (ODI), and lowest oxygen saturation. RESULTS: After MMA, 20 subjects (17 males, 3 females) with a mean age of 44 ± 12 years and body mass index of 27.4 ± 4.6 kg/m(2) showed mean decreases in AHI (53.6 ± 26.6 to 9.5 ± 7.4 events/h) and ODI (38.7 ± 30.3 to 8.1 ± 9.2 events/h; P < .001). Improvement in lateral pharyngeal wall collapse during DISE based on VOTE score correlated with the most decrease in AHI (60.0 ± 25.6 to 7.5 ± 3.4 events/h) and ODI (46.7 ± 29.8 to 5.3 ± 2 events/h; P = .002). CFD modeling showed significant positive Pearson correlations between reduction of retropalatal airflow velocity and AHI (r = 0.617, P = .04) and ODI (r = 0.773, P = .005). CONCLUSION: AHI and ODI improvement after MMA is best correlated with (1) decreased retropalatal airflow velocity modeled by CFD and (2) increased lateral pharyngeal wall stability based on VOTE scoring from DISE.

Maxillomandibular Advancement for Treatment of Obstructive Sleep Apnea: A Meta-analysis.

IMPORTANCE: Maxillomandibular advancement (MMA) is an invasive yet effective surgical option for obstructive sleep apnea (OSA) that achieves enlargement of the upper airway by physically expanding the facial skeletal framework. OBJECTIVE: To identify criteria associated with surgical outcomes of MMA using aggregated individual patient data from multiple studies. DATA SOURCES: The Cochrane Library, Scopus, Web of Science, and MEDLINE from June 1, 2014, to March 16, 2015, using the Medical Subject Heading keywords maxillomandibular advancement, orthognathic surgery, maxillary osteotomy, mandibular advancement, sleep apnea, surgical, surgery, sleep apnea syndrome, and obstructive sleep apnea. STUDY SELECTION: Inclusion criteria consisted of studies in all languages of (1) adult patients who underwent MMA as treatment for OSA; (2) report of preoperative and postoperative quantitative outcomes for the apnea-hypopnea index (AHI) and/or respiratory disturbance index (RDI); and (3) report of individual patient data. Studies of patients who underwent adjunctive procedures at the time of MMA (including tonsillectomy, uvulopalatopharyngoplasty, and partial glossectomy) were excluded. DATA EXTRACTION: Three coauthors systematically reviewed the articles and updated the review through March 16, 2015. The PRISMA statement was followed. Data were pooled using a random-effects model and analyzed from July 1, 2014, to September 23, 2015. MAIN OUTCOMES AND MEASURES: The primary outcomes were changes in the AHI and RDI after MMA for each patient. Secondary outcomes included surgical success, defined as the percentage of patients with more than 50% reduction of the AHI to fewer than 20 events/h, and OSA cure, defined as a post-MMA AHI of fewer than 5 events/h. RESULTS: Forty-five studies with individual data from 518 unique patients/interventions were included. Among patients for whom data were available, 197 of 268 (73.5%) had undergone prior surgery for OSA. Mean (SD) postoperative changes in the AHI and RDI after MMA were -47.8 (25.0) and -44.4 (33.0), respectively; mean (SE) reductions of AHI and RDI outcomes were 80.1% (1.8%) and 64.6% (4.0%), respectively; and 512 of 518 patients (98.8%) showed improvement. Significant improvements were also seen in the mean (SD) postoperative oxygen saturation nadir (70.1% [15.6%] to 87.0% [5.2%]; P < .001) and Epworth Sleepiness Scale score (13.5 [5.2] to 3.2 [3.2]; P < .001). Rates of surgical success and cure were 389 (85.5%) and 175 (38.5%), respectively, among 455 patients with AHI data and 44 (64.7%) and 13 (19.1%), respectively, among 68 patients with RDI data. Preoperative AHI of fewer than 60 events/h was the factor most strongly associated with the highest incidence of surgical cure. Nevertheless, patients with a preoperative AHI of more than 60 events/h experienced large and substantial net improvements despite modest surgical cure rates. CONCLUSIONS AND RELEVANCE: Maxillomandibular advancement is an effective treatment for OSA. Most patients with high residual AHI and RDI after other unsuccessful surgical procedures for OSA are likely to benefit from MMA.

Large maxillomandibular advancements for obstructive sleep apnea: An operative technique evolved over 30 years.

OBJECTIVE: Obstructive sleep apnea (OSA) can be a challenging disorder to treat. Maxillomandibular advancements (MMAs) generally have high success rates; however, larger advancements have higher success and cure rates. Our aim is to present and to describe the current technique used by the senior authors, which has been successful for performing large advancements, thereby improving post-operative outcomes. METHODS: The senior authors have developed and modified their maxillomandibular advancement operative techniques significantly over the past 30 years. The current version of the Riley-Powell MMA technique is described in a step-by-step fashion in this article. RESULTS: Initially, as part of the MMAs, patients underwent maxillomandibular fixation with wires, lag screws and harvested split calvarial bone grafts. The current technique utilizes plates, screws, Erich Arch Bars, and suspension wires which are left in place for 5-6 weeks. Guiding elastics are worn for the first week. The MMA technique described in this article has yielded a success rate over 90% for patients with a body mass index (BMI) <40 kg/m(2) and 81% for patients with a BMI ≥40 kg/m(2). CONCLUSION: Large advancements during maxillomandibular advancement surgeries can help improve post-operative obstructive sleep apnea outcomes.

Lateral Pharyngeal Wall Tension After Maxillomandibular Advancement for Obstructive Sleep Apnea Is a Marker for Surgical Success: Observations From Drug-Induced Sleep Endoscopy.

PURPOSE: The efficacy of maxillomandibular advancement (MMA) for obstructive sleep apnea (OSA) with anatomic airway changes has previously been studied using static imaging and endoscopy in awake subjects. The aim of the present study was to use drug-induced sleep endoscopy (DISE) to evaluate the dynamic upper airway changes in sleeping subjects before and after MMA and their association with the surgical outcome. PATIENTS AND METHODS: This was a retrospective cohort study of subjects with OSA who had undergone MMA at the Stanford University Sleep Surgery Division from July 2013 to July 2014. The subjects were included if perioperative polysomnography and DISE had been performed. The predictor variable was the perioperative DISE velum-oropharynx-tongue-epiglottis score. The outcome variables were the apnea-hypopnea index (AHI), oxygen-desaturation index (ODI), and Epworth Sleepiness Scale (ESS). A subgroup analysis was performed for the subjects who had undergone primary and secondary MMA. The statistical analyses included Cronbach's α coefficient, the McNemar test, and the independent Student t test. The P value was set at <.01. RESULTS: A total of 16 subjects (15 males, 1 female) were included in the present study, with an average age of 47 ± 10.9 years and body mass index of 29.4 ± 5.1 kg/m(2). Significant post-MMA decreases were found in the AHI (from 59.8 ± 25.6 to 9.3 ± 7.1 events/hr) and ODI (from 45 ± 29.7 to 5.7 ± 4.1 events/hr; P < .001). Greater improvement in the AHI occurred in the primary MMA group (P = .022). The post-MMA change in airway collapse was most significant at the lateral pharyngeal wall (P = .001). The subjects with the most improvement in lateral pharyngeal wall collapsibility demonstrated the largest changes in the AHI (from 60.0 ± 25.6 events/hr to 7.5 ± 3.4 events/hr) and ODI (from 46.7 ± 29.8 to 5.3 ± 2 events/hr; P = .002). CONCLUSIONS: Using DISE, we observed that after MMA, the greatest reduction in upper airway collapsibility is seen at the lateral pharyngeal wall of the oropharynx, followed by the velum, and then the tongue base. The stability of the lateral pharyngeal wall is a marker of surgical success after MMA using the AHI, ODI, and ESS.

Maxillomandibular advancement and tracheostomy for morbidly obese obstructive sleep apnea: a systematic review and meta-analysis.

OBJECTIVE: The objective of this study is to systematically review polysomnography data and sleepiness in morbidly obese (body mass index [BMI] ≥40 kg/m(2)) patients with obstructive sleep apnea (OSA) treated with either a maxillomandibular advancement (MMA) or a tracheostomy and to evaluate the outcomes. DATA SOURCES: MEDLINE, Scopus, Web of Science, and the Cochrane Library. REVIEW METHODS: A search was performed from inception through April 8, 2014, in each database. RESULTS: Six maxillomandibular advancement studies (34 patients, age 42.42 ± 9.13 years, mean BMI 44.88 ± 4.28 kg/m(2)) and 6 tracheostomy studies (14 patients, age 52.21 ± 10.40 years, mean BMI 47.93 ± 7.55 kg/m(2)) reported individual patient data. The pre- and post-MMA means ± SDs for apnea-hypopnea indices were 86.18 ± 33.25/h and 9.16 ± 7.89/h (P < .00001), and lowest oxygen saturations were 66.58% ± 16.41% and 87.03% ± 5.90% (P < .00001), respectively. Sleepiness following MMA decreased in all 5 patients for whom it was reported. The pre- and posttracheostomy mean ± SD values for apnea indices were 64.43 ± 41.35/h and 1.73 ± 2.68/h (P = .0086), oxygen desaturation indices were 69.20 ± 26.10/h and 41.38 ± 36.28/h (P = .22), and lowest oxygen saturations were 55.17% ± 16.46% and 79.83% ± 4.36% (P = .011), respectively. Two studies reported outcomes for Epworth Sleepiness Scale for 5 patients, with mean ± SD values of 18.80 ± 4.02 before tracheostomy and 2.80 ± 2.77 after tracheostomy (P = .0034). CONCLUSION: Data for MMA and tracheostomy as treatment for morbidly obese, adult OSA patients are significantly limited. We caution surgeons about drawing definitive conclusions from these limited studies; higher level studies are needed.

Improved sleep MRI at 3 tesla in patients with obstructive sleep apnea.

PURPOSE: To describe a real-time MR imaging platform for synchronous, multi-planar visualization of upper airway collapse in obstructive sleep apnea at 3 Tesla (T) to promote natural sleep with an emphasis on lateral wall visualization. MATERIALS AND METHODS: A real-time imaging platform was configured for sleep MR imaging which used a cartesian, partial k-space gradient-echo sequence with an inherent temporal resolution of 3 independent slices every 2 s. Combinations of axial, mid-sagittal, and coronal scan planes were acquired. The system was tested in five subjects with polysomnography-proven obstructive sleep apnea during sleep, with synchronous acquisition of respiratory effort and combined oral-nasal airflow data. RESULTS: Sleep was initiated and maintained to allow demonstration of sleep-induced, upper airway collapse as illustrated in two subjects when using a real-time, sleep MR imaging platform at 3T. Lateral wall collapse could not be visualized on mid-sagittal imaging alone and was best characterized on multiplanar coronal and axial imaging planes. CONCLUSION: Our dedicated sleep MR imaging platform permitted an acoustic environment of constant "white noise" which was conducive to sleep onset and sleep maintenance in obstructive sleep apnea patients at 3T. Apneic episodes, specifically the lateral walls, were more accurately characterized with synchronous, multiplanar acquisitions.

Peripheral neuropathology of the upper airway in obstructive sleep apnea syndrome.

Obstructive sleep apnea syndrome (OSAS) is a common sleep disorder that leads to significant morbidity and mortality without adequate treatment. Though much emphasis on the pathogenesis of OSAS has been placed on a narrow upper airway space and associated muscular factors, possible neuropathy of the upper airway has not been fully elucidated. Increasing peer reviewed evidence suggests involvement of neurologic lesions of the upper airway in OSAS patients. In this article, we review the etiology and pathophysiology of OSAS, the evidence and possible mechanisms leading to upper airway neuropathy, and the relationship between upper airway neuropathy and OSAS. Further studies should focus on the long term effects of the upper airway neuropathy as related to the duration and severity of snoring and or apnea, and also on the potential methods of prevention and management of the neuropathy in sleep disordered breathing.

Systematic analysis of cephalometry in obstructive sleep apnea in Asian children.

OBJECTIVES/HYPOTHESIS: This study was designed to systematically analyze the relationship between a cephalometric analysis and the apnea-hypopnea index in a group of Asian children with obstructive sleep apnea. STUDY DESIGN: Retrospective study. METHODS: Data were collected from 56 children with obstructive sleep apnea who were between 3 and 13 years old. Each child underwent attended overnight polysomnography and cephalometry. We measured nine angles, 10 lines, and two ratios as well as adenoid size on each cephalometric film. Data included five segments of the upper airway: nasal cavity (segment 1), nasopharyngeal space (segment 2), retropalatal space (segment 3), retroglossal space and hyoid (segment 4), and oral cavity-related space (segment 5). RESULTS: Four cephalometric anthropomorphic findings (Gn-Go-H, MP-H, MPH/GnGo, Ad/Na) were related to the apnea-hypopnea index. Three of the four parameters belonged to segment 4, indicating the importance of hyoid position in pediatric obstructive sleep apnea. CONCLUSIONS: This study showed that segment 4 was the most important segment affecting the apnea-hypopnea index. Most of the cephalometric parameters in segment 4 did not show a difference from the results of Caucasian groups, except that mandibular length and position appeared to have more positive findings in the Caucasian results. In segment 2, the apnea-hypopnea index was less affected by the skull base-related parameters in our data. The reason why the other segments appeared to play a lesser role in pediatric obstructive sleep apnea might due to the limitations of two-dimensional imaging. Further cephalometric studies with anterior-posterior view and on the differences between Caucasian and Asian children are mandatory.

Patterns in pharyngeal airflow associated with sleep-disordered breathing.

OBJECTIVE: To establish the feasibility of a noninvasive method to identify pharyngeal airflow characteristics in sleep-disordered breathing. METHODS: Four patients with sleep-disordered breathing who underwent surgery or used positive airway pressure devices and four normal healthy controls were studied. Three-dimensional CT imaging and computational fluid dynamics modeling with standard steady-state numerical formulation were used to characterize pharyngeal airflow behavior in normals and pre-and post-treatment in patients. Dynamic flow simulations using an unsteady approach were performed in one patient. RESULTS: The pre-treatment pharyngeal airway below the minimum cross-sectional area obstruction site showed airflow separation. This generated recirculation airflow regions and enhanced turbulence zones where vortices developed. This interaction induced large fluctuations in airflow variables and increased aerodynamic forces acting on the pharyngeal wall. At post-treatment, for the same volumetric flow rate, airflow field instabilities vanished and airflow characteristics improved. Mean maximum airflow velocity during inspiration reduced from 18.3±5.7 m/s pre-treatment to 6.3±4.5 m/s post-treatment (P=0.002), leading to a reduction in maximum wall shear stress from 4.8±1.7 Pa pre-treatment to 0.9±1.0 Pa post-treatment (P=0.01). The airway resistance improved from 4.3±1.4 Pa/L/min at pre-treatment to 0.7±0.7 Pa/L/min at post-treatment (P=0.004). Post-treatment airflow characteristics were not different from normal controls (all P ≥ 0.39). CONCLUSION: This study demonstrates that pharyngeal airflow variables may be derived from CT imaging and computational fluid dynamics modeling, resulting in high quality visualizations of airflow characteristics of axial velocity, static pressure, and wall shear stress in sleep-disordered breathing.

Large eddy simulation of the pharyngeal airflow associated with obstructive sleep apnea syndrome at pre and post-surgical treatment.

Obstructive Sleep Apnea Syndrome (OSAS) is the most common sleep-disordered breathing medical condition and a potentially life-threatening affliction. Not all the surgical or non-surgical OSAS therapies are successful for each patient, also in part because the primary factors involved in the etiology of this disorder are not completely understood. Thus, there is a need for improving both diagnostic and treatment modalities associated with OSAS. A verified and validated (in terms of mean velocity and pressure fields) Large Eddy Simulation approach is used to characterize the abnormal pharyngeal airflow associated with severe OSAS and its interaction with the airway wall in a subject who underwent surgical treatment. The analysis of the unsteady flow at pre- and post-treatment is used to illustrate the airflow dynamics in the airway associated with OSAS and to reveal as well, the changes in the flow variables after the treatment. At pre-treatment, large airflow velocity and wall shear stress values were found at the obstruction site in all cases. Downstream of obstruction, flow separation generated flow recirculation regions and enhanced the turbulence production in the jet-like shear layers. The interaction between the generated vortical structures and the pharyngeal airway wall induced large fluctuations in the pressure forces acting on the pharyngeal wall. After the surgery, the flow field instabilities vanished and both airway resistance and wall shear stress values were significantly reduced.

Maxillary, mandibular, and chin advancement: treatment planning based on airway anatomy in obstructive sleep apnea.

Surgical correction of obstructive sleep apnea (OSA) syndrome involves understanding a number of parameters, of which the 3-dimensional airway anatomy is important. Visualization of the upper airway based on cone beam computed tomography scans and automated computer analysis is an aid in understanding normal and abnormal airway conditions and their response to surgery. The goal of surgical treatment of OSA syndrome is to enlarge the velo-oropharyngeal airway by anterior/lateral displacement of the soft tissues and musculature by maxillary, mandibular, and possibly, genioglossus advancement. Knowledge of the specific airway obstruction and characteristics based on 3-dimensional studies permits a directed surgical treatment plan that can successfully address the area or areas of airway obstruction. The end occlusal result can be improved when orthodontic treatment is combined with the surgical plan. The individual with OSA, though, is more complicated than the usual orthognathic patient, and both the medical condition and treatment length need to be judiciously managed when OSA and associated conditions are present. The perioperative management of the patient with OSA is more complex and the margin for error is reduced, and this needs to be taken into consideration and the care altered as indicated.

Sleepy driving.

Sleepiness and drowsiness are neurophysiologic states that may cause attenuation of vigilance and slowing of reaction times, and thus increase the risks of driving. This article reviews selected peer-reviewed publications from the past and present body of knowledge regarding sleepiness and drowsiness while driving and related accidents, injuries, and possible death. Comparative studies of driving drunk and driving sleepy are reviewed because both exhibit similarly dangerous driving behaviors. It is hoped that some of the information from this article could provide new interest in the necessity of education for sleepy drivers.

Contemporary surgery for obstructive sleep apnea syndrome.

Surgical treatment of obstructive sleep apnea syndrome (OSAS) has been available in some form for greater than three decades. Early management for airway obstruction during sleep relied on tracheotomy which although life saving was not well accepted by patients. In the early eighties two new forms of treatment for OSAS were developed. Surgically a technique described as a uvulopalatopharyngoplasty (UPPP) was used to treat the retropalatal region for snoring and sleep apnea. Concurrently sleep medicine developed a nasal continuous positive airway pressure (CPAP) device to manage nocturnal airway obstruction. Both of these measures were used to expand and stabilize the pharyngeal airway space during sleep. The goal for each technique was to limit or alleviate OSAS. Almost 30 yr later these two treatment modalities continue to be the mainstay of contemporary treatment. As expected, CPAP device technology improved over time along with durable goods. Surgery followed suit and additional techniques were developed to treat soft and bony structures of the entire upper airway (nose, palate and tongue base). This review will only focus on the contemporary surgical methods that have demonstrated relatively consistent positive clinical outcomes. Not all surgical and medical treatment modalities are successful or even partially successful for every patient. Advances in the treatment of OSAS are hindered by the fact that the primary etiology is still unknown. However, both medicine and surgery continue to improve diagnostic and treatment methods. Methods of diagnosis as well as treatment regimens should always include both medical and surgical collaborations so the health and quality of life of our patients can best be served.

Resting energy expenditure in adults with sleep disordered breathing.

OBJECTIVE: To examine the association between sleep disordered breathing severity and resting energy expenditure (REE). DESIGN: Cross-sectional. SETTING: University-based academic medical center. PARTICIPANTS: Two hundred twelve adults with signs or symptoms of sleep disordered breathing underwent medical history, physical examination, level I attended polysomnography, and determination of REE using an indirect calorimeter. MAIN OUTCOME MEASURE: Mean REE. RESULTS: Seventy-one percent (151 of 212) of the study population were male, and the mean (SD) age was 42.3 (12.6) years. The mean (SD) body mass index, calculated as weight in kilograms divided by height in meters squared, was 28.3 (7.3). The mean (SD) apnea-hypopnea index was 25.4 (27.2), and the lowest oxygen saturation during the sleep study was 86.9% (9.5%). The mean (SD) REE was 1763 (417) kcal/d. Analysis of variance and univariate regression analysis showed an association between REE and several measures of sleep disordered breathing severity that persisted after adjustment for age, sex, and self-reported health status in multiple regression analysis. Only REE and the apnea-hypopnea index demonstrated an independent association after additional adjustment for body mass index (or body weight and height separately). This association did not differ between individuals with normal vs elevated body mass index. CONCLUSIONS: Sleep disordered breathing severity is associated with REE. Although this association is largely confounded by body weight, there is an independent association with the apnea-hypopnea index.

Facial skeletal surgery in the management of adult obstructive sleep apnea syndrome.

Obstructive sleep apnea (OSA) remains a significant public health problem because of its neurocognitive sequelae. Additionally, with persistent obstruction, it has an impact on the cardiovascular system, leading to hypertension and cardiac failure as one of its causative or comorbid factors. For the surgeon managing OSA, there is a stepwise sequence of surgical procedures, from improving nasal airflow to facial skeletal maxillary-mandibular advancement, with the cumulative goal of volumetrically increasing the retropharyngeal airway space. Familiarity with conventional orthognathic principles is essential in achieving this goal.

Sleepy driver near-misses may predict accident risks.

STUDY OBJECTIVES: To quantify the prevalence of self-reported near-miss sleepy driving accidents and their association with self-reported actual driving accidents. DESIGN: A prospective cross-sectional internet-linked survey on driving behaviors. SETTING: Dateline NBC News website. RESULTS: Results are given on 35,217 (88% of sample) individuals with a mean age of 37.2 +/- 13 years, 54.8% women, and 87% white. The risk of at least one accident increased monotonically from 23.2% if there were no near-miss sleepy accidents to 44.5% if there were > or = 4 near-miss sleepy accidents (P < 0.0001). After covariate adjustments, subjects who reported at least one near-miss sleepy accident were 1.13 (95% CI, 1.10 to 1.16) times as likely to have reported at least one actual accident as subjects reporting no near-miss sleepy accidents (P < 0.0001). The odds of reporting at least one actual accident in those reporting > or = 4 near-miss sleepy accidents as compared to those reporting no near-miss sleepy accidents was 1.87 (95% CI, 1.64 to 2.14). Furthermore, after adjustments, the summary Epworth Sleepiness Scale (ESS) score had an independent association with having a near-miss or actual accident. An increase of 1 unit of ESS was associated with a covariate adjusted 4.4% increase of having at least one accident (P < 0.0001). CONCLUSION: A statistically significant dose-response was seen between the numbers of self-reported sleepy near-miss accidents and an actual accident. These findings suggest that sleepy near-misses may be dangerous precursors to an actual accident.

Incidence of complications in radiofrequency treatment of the upper airway.

OBJECTIVES: To investigate the incidence of complications after temperature-controlled radiofrequency (TCRF) treatment of the inferior turbinates, palate, and tongue. To compare these complication rates with those reported in the literature. STUDY DESIGN: Prospective, observational study. METHODS: All patients treated with TCRF to the inferior turbinates, palate, and tongues during a 12-month period were included. Data were collected for parameters of energy delivery and the development of complications. RESULTS: One hundred thirty-six patients were treated with a total of 470 TCRF lesions. The overall incidence of minor complications was 1.2% (6/470 lesions); there were no complications of moderate or major severity. CONCLUSION: The incidence of minor complications after TCRF in this series was low, and there were no complications of greater severity. These findings are in stark contrast with some previously published papers with higher complication rates. These significantly higher rates may be caused by a marked learning curve, problems in patient selection and the technique of application, excessive energy delivery, and perioperative management.

Preliminary observations on the effects of sleep time in a sleep restriction paradigm.

OBJECTIVE: To evaluate of the effect of 7 days of sleep restriction--with sleep placed at the beginning of night or early morning hours - on sleep variables, maintenance of wakefulness test, and serum leptin. METHODS: After screening young adults with questionnaires and actigraphy for 1 week, eight young adult males were recruited to participate in a sleep restriction study. The subjects were studied for baseline data for 2.5 days, with 8.5 h per night in bed, and then over 7 days of sleep restriction to 4 h per night with a 22:30 h bedtime for half the group and a 02:15 h bedtime for the other half. At the end of study, after one night of ad libitum sleep, subjects again had 2 days of 8.5 h in bed. Wakefulness was continuously verified and tests, including Maintenance of Wakefulness (MWT), were performed during the scheduled wake time. Blood was drawn six times throughout the 24 h of the 7th day of sleep restriction and after 2 days of the post-restriction schedule. RESULTS: There was individual variability in response to sleep restriction, but independent of group distribution, MWT was significantly affected by sleep restriction, with the early morning sleep group having less decrease in MWT score. Sleep efficiency was also better in this group, which also had shorter sleep latency. Independent of group distribution there was a greater increase in the percentage of slow wave sleep than rapid eye movement sleep, despite a clear internal variability and variability between subjects. Peak serum leptin was significantly decreased with 7 days of sleep restriction for all subjects. CONCLUSION: Sleep restriction to 4 h affected all subjects, but there were individual and group differences in MWT and sleep data. In this group of young adult males (mean age 19 years), there was a better overall adaptation to the early morning sleep, perhaps related to the general tendency in most adolescents to present some phase-delay during late teen-aged years.