520-d Isolation and confinement simulating a flight to Mars reveals heightened immune responses and alterations of leukocyte phenotype.

During interplanetary exploration, chronic stress caused by long term isolation and confinement in the spacecraft is one of the major concerns of physical and psychological health of space travelers. And for human on Earth, more and more people live in an isolated condition, which has become a common social problem in modern western society. Collective evidences have indicated prolonged chronic stress could bring big influence to human immune function, which may lead to a variety of health problems. However, to what extent long-term isolation can affect the immune system still remains largely unknow. A simulated 520-d Mars mission provided an extraordinary chance to study the effect of prolonged isolation. Six healthy males participated in this mission and their active neuroendocrine and immune conditions were studied with saliva and blood samples from all participants on chosen time points during the isolation period. As a typical neuroendocrine parameter, stress hormone cortisol was measured in the morning saliva samples. Immune phenotype changes were monitored through peripheral leukocyte phenotype analysis. Using an ex vivo viral infection simulation assay we assessed the immune response changes characterized by the ability to produce representative endogenous pro-inflammatory cytokines. The results of this study revealed elevated cortisol levels, increased lymphocyte amount and heightened immune responses, suggesting that prolonged isolation acting as chronic stressors are able to trigger leukocyte phenotype changes and poorly controlled immune responses.

Sleep loss reduces diurnal rhythm amplitude of leptin in healthy men.

The aim of the current study was to investigate the effects of sleep loss on the diurnal rhythm of circulating leptin levels. An indwelling forearm catheter was used to sample blood at 90-min intervals for a total of 120 h, which included 88 h of sustained sleeplessness, in 10 healthy men. The diurnal amplitude of leptin was reduced during total sleep deprivation and returned toward normal during the period of recovery sleep. This finding provides evidence that sleep influences the nocturnal leptin profile, and may have implications for the understanding of the role of sleep in metabolic regulation and the aetiologies of obesity and the night eating syndrome.

Caffeine eliminates psychomotor vigilance deficits from sleep inertia.

STUDY OBJECTIVES: This study sought to establish the effects of caffeine on sleep inertia, which is the ubiquitous phenomenon of cognitive performance impairment, grogginess and tendency to return to sleep immediately after awakening. DESIGN: 28 normal adult volunteers were administered sustained low-dose caffeine or placebo (randomized double-blind) during the last 66 hours of an 88-hour period of extended wakefulness that included seven 2-hour naps during which polysomnographical recordings were made. Every 2 hours of wakefulness, and immediately after abrupt awakening from the naps, psychomotor vigilance performance was tested. SETTING: N/A. PARTICIPANTS: N/A. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: In the placebo condition, sleep inertia was manifested as significantly impaired psychomotor vigilance upon awakening from the naps. This impairment was absent in the caffeine condition. Caffeine had only modest effects on nap sleep. CONCLUSIONS: Caffeine was efficacious in overcoming sleep inertia. This suggests a reason for the popularity of caffeine-containing beverages after awakening. Caffeine's main mechanism of action on the central nervous system is antagonism of adenosine receptors. Thus, increased adenosine in the brain upon awakening may be the cause of sleep inertia.

Neuroimmunologic aspects of sleep and sleep loss.

The complex and intimate interactions between the sleep and immune systems have been the focus of study for several years. Immune factors, particularly the interleukins, regulate sleep and in turn are altered by sleep and sleep deprivation. The sleep-wake cycle likewise regulates normal functioning of the immune system. Although a large number of studies have focused on the relationship between the immune system and sleep, relatively few studies have examined the effects of sleep deprivation on immune parameters. Studies of sleep deprivation's effects are important for several reasons. First, in the 21st century, various societal pressures require humans to work longer and sleep less. Sleep deprivation is becoming an occupational hazard in many industries. Second, to garner a greater understanding of the regulatory effects of sleep on the immune system, one must understand the consequences of sleep deprivation on the immune system. Significant detrimental effects on immune functioning can be seen after a few days of total sleep deprivation or even several days of partial sleep deprivation. Interestingly, not all of the changes in immune physiology that occur as a result of sleep deprivation appear to be negative. Numerous medical disorders involving the immune system are associated with changes in the sleep-wake physiology--either being caused by sleep dysfunction or being exacerbated by sleep disruption. These disorders include infectious diseases, fibromyalgia, cancers, and major depressive disorder. In this article, we will describe the relationships between sleep physiology and the immune system, in states of health and disease. Interspersed will be proposals for future research that may illuminate the clinical relevance of the relationships between sleeping, sleep loss and immune function in humans.

Sustained attention performance during sleep deprivation: evidence of state instability.

Nathaniel Kleitman was the first to observe that sleep deprivation in humans did not eliminate the ability to perform neurobehavioral functions, but it did make it difficult to maintain stable performance for more than a few minutes. To investigate variability in performance as a function of sleep deprivation, n = 13 subjects were tested every 2 hours on a 10-minute, sustained-attention, psychomotor vigilance task (PVT) throughout 88 hours of total sleep deprivation (TSD condition), and compared to a control group of n = 15 subjects who were permitted a 2-hour nap every 12 hours (NAP condition) throughout the 88-hour period. PVT reaction time means and standard deviations increased markedly among subjects and within each individual subject in the TSD condition relative to the NAP condition. TSD subjects also had increasingly greater performance variability as a function of time on task after 18 hours of wakefulness. During sleep deprivation, variability in PVT performance reflected a combination of normal timely responses, errors of omission (i.e., lapses), and errors of commission (i.e., responding when no stimulus was present). Errors of omission and errors of commission were highly intercorrelated across deprivation in the TSD condition (r = 0.85, p = 0.0001), suggesting that performance instability is more likely to include compensatory effort than a lack of motivation. The marked increases in PVT performance variability as sleep loss continued supports the "state instability" hypothesis, which posits that performance during sleep deprivation is increasingly variable due to the influence of sleep initiating mechanisms on the endogenous capacity to maintain attention and alertness, thereby creating an unstable state that fluctuates within seconds and that cannot be characterized as either fully awake or asleep.

Absence of diurnal variation of C-reactive protein concentrations in healthy human subjects.

BACKGROUND: The concentration of C-reactive protein (CRP) in otherwise healthy subjects has been shown to predict future risk of myocardial infarction and stroke. CRP is synthesized by the liver in response to interleukin-6, the serum concentration of which is subject to diurnal variation. METHODS: To examine the existence of a time-of-day effect for baseline CRP values, we determined CRP concentrations in hourly blood samples drawn from healthy subjects (10 males, 3 females; age range, 21-35 years) during a baseline day in a controlled environment (8 h of nighttime sleep). RESULTS: Overall CRP concentrations were low, with only three subjects having CRP concentrations >2 mg/L. Comparison of raw data showed stability of CRP concentrations throughout the 24 h studied. When compared with cutoff values of CRP quintile derived from population-based studies, misclassification of greater than one quintile did not occur as a result of diurnal variation in any of the subjects studied. Nonparametric ANOVA comparing different time points showed no significant differences for both raw and z-transformed data. Analysis for rhythmic diurnal variation using a method fitting a cosine curve to the group data was negative. CONCLUSIONS: Our data show that baseline CRP concentrations are not subject to time-of-day variation and thus help to explain why CRP concentrations are a better predictor of vascular risk than interleukin-6. Determination of CRP for cardiovascular risk prediction may be performed without concern for diurnal variation.

Soluble TNF-alpha receptor 1 and IL-6 plasma levels in humans subjected to the sleep deprivation model of spaceflight.

BACKGROUND: The extent to which sleep loss may predispose astronauts to a state of altered immunity during extended space travel prompts evaluation with ground-based models. OBJECTIVE: We sought to measure plasma levels of selected cytokines and their receptors, including the putative sleep-regulation proteins soluble TNF-alpha receptor (sTNF-alpha R) I and IL-6, in human subjects undergoing 2 types of sleep deprivation during environmental confinement with performance demands. METHODS: Healthy adult men (n = 42) were randomized to schedules that varied in severity of sleep loss: 4 days (88 hours) of partial sleep deprivation (PSD) involving two 2-hour naps per day or 4 days of total sleep deprivation (TSD). Plasma samples were obtained every 6 hours across 5 days and analyzed by using enzyme-linked immunoassays for sTNF-alpha RI, sTNF-alpha RII, IL-6, soluble IL-2 receptor, IL-10, and TNF-alpha. RESULTS: Interactions between the effects of time and sleep deprivation level were detected for sTNF-alpha RI and IL-6 but not for sTNF-alpha RII, soluble IL-2 receptor, IL-10, and TNF-alpha. Relative to the PSD condition, subjects in the TSD condition had elevated plasma levels of sTNF-alpha RI on day 2 (P =.04), day 3 (P =.01), and across days 2 to 4 of sleep loss (P =.01) and elevated levels of IL-6 on day 4 (P =.04). CONCLUSIONS: Total sleep loss produced significant increases in plasma levels of sTNF-alpha RI and IL-6, messengers that connect the nervous, endocrine, and immune systems. These changes appeared to reflect elevations of the homeostatic drive for sleep because they occurred in TSD but not PSD, suggesting that naps may serve as the basis for a countermeasures approach to prolonged spaceflight.

Time-on-task decrements in "steer clear" performance of patients with sleep apnea and narcolepsy.

Loss of attention with time-on-task reflects the increasing instability of the waking state during performance in experimentally induced sleepiness. To determine whether patients with disorders of excessive sleepiness also displayed time-on-task decrements indicative of wake state instability, visual sustained attention performance on "Steer Clear," a computerized simple RT driving simulation task, was compared among 31 patients with untreated sleep apnea, 16 patients with narcolepsy, and 14 healthy control subjects. Vigilance decrement functions were generated by analyzing the number of collisions in each of six four-minute periods of Steer Clear task performance in a mixed-model analysis of variance and linear regression equations. As expected, patients had more Steer Clear collisions than control subjects (p=0.006). However, the inter-subject variability in errors among the narcoleptic patients was four-fold that of the apnea patients, and 100-fold that of the controls volunteers; the variance in errors among untreated apnea patients was 27-times that of controls. The results of transformed collision data revealed main effects for group (p=0.006), time-on-task (p=0.001), and a significant interaction (p=0.022). Control subjects showed no clear evidence of increasing collision errors with time-on-task (adjusted R2=0.22), while apnea patients showed a trend toward vigilance decrement (adjusted R2=0.42, p=0.097), and narcolepsy patients evidenced a robust linear vigilance decrement (adjusted R2=0.87, p=0.004). The association of disorders of excessive somnolence with escalating time-on-task decrements makes it imperative that when assessment of neurobehavioral performance is conducted in patients, it involves task durations and analyses that will evaluate the underlying vulnerability of potentially sleepy patients to decrements over time in tasks that require sustained attention and timely responses, both of which are key components in safe driving performance.

A comparative model: reaction time performance in sleep-disordered breathing versus alcohol-impaired controls.

OBJECTIVES/HYPOTHESIS: Patients with sleep-disordered breathing have reaction time deficits that may lead to catastrophic accidents and loss of life. Although safety guidelines do not exist for unsafe levels of sleepiness, they have been established for unsafe levels of alcohol consumption. Since reaction time performance is altered in both, we prospectively used seven measures of reaction time performance as a comparative model in alcohol-challenged normal subjects with corresponding measures in subjects with sleep-disordered breathing. STUDY DESIGN: Institutional Review Board-approved, nonrandomized prospective controlled study. METHODS: Eighty healthy volunteers (29.1+/-7.5 y of age, 56.3% female subjects) performed four reaction time trials using a psychomotor test at baseline and at three subsequent rising alcohol-influenced time points. The same test without alcohol was given to 113 subjects (47.2+/-10.8 y of age, 19.3% female subjects) with mild to moderate sleep-disordered breathing. RESULTS: Mean blood alcohol concentrations (BACs) in the alcohol-influenced subjects at baseline and three trials were 0, 0.057, 0.080, and 0.083 g/dL. The sleep-disordered subjects had mean respiratory disturbance indices of 29.2 events per hour of sleep. On all seven reaction time measures, their performance was worse than that of the alcohol subjects when BACs were 0.057 g/dL. For three of the measures, the sleep-disordered subjects performed as poorly as or worse than the alcohol subjects when alcohol levels were 0.080 g/dL. These results could not be explained by sex or age differences. CONCLUSION: The data demonstrate that sleep-disordered subjects in this study (with a mean age of 47 y) with mild to moderate sleep-disordered breathing had worse test reaction time performance parameters than healthy, nonsleepy subjects (with a mean age of 29 y) whose BAC is illegally high for driving a commercial motor vehicle in California. This comparative model points out the potential risks of daytime sleepiness in those with sleep-disordered breathing relative to a culturally accepted standard of impairment.

Dose-response relationship between sleep duration and human psychomotor vigilance and subjective alertness.

Although it has been well documented that sleep is required for human performance and alertness to recover from low levels after prolonged periods of wakefulness, it remains unclear whether they increase in a linear or asymptotic manner during sleep. It has been postulated that there is a relation between the rate of improvement in neurobehavioral functioning and rate of decline of slow-wave sleep and/or slow-wave activity (SWS/SWA) during sleep, but this has not been verified. Thus, a cross-study comparison was conducted in which dose-response curves (DRCs) were constructed for Stanford Sleepiness Scale (SSS) and Psychomotor Vigilance Task (PVT) tests taken at 1000 hours by subjects who had been allowed to sleep 0 hours, 2 hours, 5 hours or 8 hours the previous night. We found that the DRCs to each PVT metric improved in a saturating exponential manner, with recovery rates that were similar [time constant (T) approximately 2.14 hours] for all the metrics. This recovery rate was slightly faster than, though not statistically significantly different from, the reported rate of SWS/SWA decline (T approximately 2.7 hours). The DRC to the SSS improved much more slowly than psychomotor vigilance, so that it could be fit equally well by a linear function (slope = -0.26) or a saturating exponential function (T = 9.09 hours). We conclude that although SWS/SWA, subjective alertness, and a wide variety of psychomotor vigilance metrics may all change asymptotically during sleep, it remains to be determined whether the underlying physiologic processes governing their expression are different.

Rapid eye movement sleep changes during the adaptation night in combat veterans with posttraumatic stress disorder.

BACKGROUND: Hyperarousal in posttraumatic stress disorder (PTSD) is manifested during sleep as well as waking. Elevated rapid eye movement sleep (REMS) phasic activity, likely signifying central nervous system alerting, has been identified in PTSD. The authors reasoned that PTSD compared to control subjects would show particularly increased REMS phasic activity on the first night of polysomnography, with adaptation to a novel environment. METHODS: First-night polysomnograms of 17 veterans with PTSD were compared with those of 11 control subjects. Sleep was also studied in subsets of both groups over two nights. RESULTS: On the first night, the PTSD subjects had a higher density of rapid eye movements in the first REMS period. This measure was increased on the first compared to the second night, but there was no interaction effect between night and group. CONCLUSIONS: REMS changes are again demonstrated in veterans with PTSD. Introduction to a novel environment activated a REMS phasic process, but not differentially in PTSD compared to control subjects.

Commentary: future considerations for models of human neurobehavioral function.

Modeling human neurobehavioral functions has the goal of identifying work-rest schedules that are safer and more productive. The models of Folkard et al. and of Jewett and Kronauer illustrate excellent progress toward this goal. Examination of these models reveals four additional areas that need to be addressed to facilitate continued development of accurate models of neurobehavioral functions. (1) The choice of neurobehavioral metrics may have a significant influence on model development. The lack of correlation among different neurobehavioral measures may make comparisons of models difficult. Many neurobehavioral measures are confounded by secondary and random error variance that can lead to model distortion. Although different models may ultimately be required for different neurobehavioral functions, measures that have been extensively validated to be sensitive to circadian variation and sleep loss should take priority in model development. (2) Because error variance in neurobehavioral outcomes can be substantial in uncontrolled environments, model validation should proceed from controlled laboratory protocols to real-world scenarios. Once validated, the ability of a model to predict field data can be tested. (3) While neurobehavioral models have been developed to predict behavior over time (i.e., within-subjects), to be useful in the real world, models will also ultimately have to provide estimates of between-subject variation in vulnerability to neurobehavioral dysfunction during night work or sleep loss (e.g., younger versus older workers). (4) Finally, to be theoretically accurate and practically useful, models of human neurobehavioral functions should be able to predict both cumulative effects (i.e., across days or weeks) and the influence of countermeasures (e.g., light, naps, caffeine).

Flight controller alertness and performance during spaceflight shiftwork operations.

Decreased alertness and performance associated with fatigue, sleep loss, and circadian disruption are issues faced by a diverse range of shiftwork operations personnel. During Space Transportation System (STS) operations, Mission Operations Directorate (MOD) personnel provide 24-hr. coverage of critical tasks. A joint NASA Johnson Space Center and NASA Ames Research Center project was undertaken to examine these issues in flight controllers during MOD shiftwork operations. An initial operational test of procedures and measures was conducted during the STS-53 mission in December 1992. The study measures included a Background Questionnaire, a subjective daily logbook completed on a 24-hour basis (to report sleep patterns, work periods, etc.), and an 8 minute performance and mood test battery administered at the beginning, middle, and end of each shift period. Seventeen flight controllers representing the 3 Orbit shifts participated. The initial results clearly support the need for further data collection during other STS missions to document baseline levels of alertness and performance during MOD shiftwork operations. Countermeasure strategies specific to the MOD environment are being developed to minimize the adverse effects of fatigue, sleep loss, and circadian disruption engendered by shiftwork operations. These issues are especially pertinent for the night shift operations and the acute phase advance required for the transition of day shift personnel into the night for shuttle launch. Implementation and evaluation of the countermeasure strategies to maximize alertness and performance is planned. As STS missions extend to further EDO (extended duration orbiters), and timelines and planning for 24-hour Space Station operations continue, alertness and performance issues related to sleep and circadian disruption will remain highly relevant in the MOD environment.

Rotating shiftwork schedules: can we enhance physician adaptation to night shifts?

OBJECTIVES: To evaluate the effectiveness of a broad, literature-based night shiftwork intervention for enhancement of emergency physicians' (EPs') adaptation to night rotations. METHODS: A prospective, double-blind, active placebo-controlled study was conducted on 6 attending physicians in a university hospital ED. Three data sets were collected under the following conditions: baseline, after active placebo intervention, and after experimental intervention. In each condition, data were collected when the physicians worked both night and day shifts. Measurements included ambulatory polysomnographic recordings of the main sleep periods, objective performance tests administered several times during the subjects' shifts, and daily subjective ratings of the subjects' sleep, moods, and intervention use. RESULTS: The subjects slept an average of 5 hr 42 min across all conditions. After night shifts, the subjects slept significantly less than they did after day shifts (5 hr 13 min vs 6 hr 20 min; p < 0.05). The physicians' vigilance reaction times and times for intubation of a mannequin were significantly slower during night shifts than they were during day shifts (p = 0.007 and p < 0.04, respectively), but performances on ECG analysis did not significantly differ between night and day shifts. Mood ratings were significantly more negative during night shifts than they were during day shifts (more sluggish p < 0.04, less motivated p < 0.03, and less clear thinking p < 0.04). The strategies in the experimental intervention were used 85% of the time according to logbook entries. The experimental and active placebo interventions did not significantly improve the physician's performance, or mood on the night shift, although the subjects slept more after both interventions. CONCLUSIONS: Although the experimental intervention was successfully implemented, it failed to significantly improve attending physicians' sleep, performance, or mood on night shifts. A decrease in speed of intubation, vigilance reaction times, and subjective alertness was evident each time the physicians rotated through the night shift. These findings plus the limited sleep across all conditions and shifts suggest that circadian-mediated disruptions of waking neurobehavioral functions and sleep deprivation are problems in EPs.

Self-hypnosis training as an adjunctive treatment in the management of pain associated with sickle cell disease.

A cohort of patients with sickle cell disease, consisting of children, adolescents, and adults, who reported experiencing three or more episodes of vaso-occlusive pain the preceding year, were enrolled in a prospective two-period treatment protocol. Following a 4-month conventional treatment baseline phase, a supplemental cognitive-behavioral pain management program that centered on self-hypnosis was implemented over the next 18 months. Frequency of self-hypnosis group straining sessions began at once per week for the first 6 months, became biweekly for the next 6 months, and finally occurred once every third week for the remaining 6 months. Results indicate that the self-hypnosis intervention was associated with a significant reduction in pain days. Both the proportion of "bad sleep" nights and the use of pain medications also decreased significantly during the self-hypnosis treatment phase. However, participants continued to report disturbed sleep and to require medications on those days during which they did experience pain. Findings further suggest that the overall reduction in pain frequency was due to the elimination of less severe episodes of pain. Non-specific factors may have contributed to the efficacy of treatment. Nevertheless, the program clearly demonstrates that an adjunctive behavioral treatment for sickle cell pain, involving patient self-management and regular contact with a medical self-hypnosis team, can be beneficial in reducing recurrent, unpredictable episodes of pain in a patient population for whom few safe, cost-effective medical alternatives exist.

Cumulative sleepiness, mood disturbance, and psychomotor vigilance performance decrements during a week of sleep restricted to 4-5 hours per night.

To determine whether a cumulative sleep debt (in a range commonly experienced) would result in cumulative changes in measures of waking neurobehavioral alertness, 16 healthy young adults had their sleep restricted 33% below habitual sleep duration, to an average 4.98 hours per night [standard deviation (SD) = 0.57] for seven consecutive nights. Subjects slept in the laboratory, and sleep and waking were monitored by staff and actigraphy. Three times each day (1000, 1600, and 2200 hours) subjects were assessed for subjective sleepiness (SSS) and mood (POMS) and were evaluated on a brief performance battery that included psychomotor vigilance (PVT), probed memory (PRM), and serial-addition testing, Once each day they completed a series of visual analog scales (VAS) and reported sleepiness and somatic and cognitive/emotional problems. Sleep restriction resulted in statistically robust cumulative effects on waking functions. SSS ratings, subscale scores for fatigue, confusion, tension, and total mood disturbance from the POMS and VAS ratings of mental exhaustion and stress were evaluated across days of restricted sleep (p = 0.009 to p = 0.0001). PVT performance parameters, including the frequency and duration of lapses, were also significantly increased by restriction (p = 0.018 to p = 0.0001). Significant time-of-day effects were evident in SSS and PVT data, but time-of-day did not interact with the effects of sleep restriction across days. The temporal profiles of cumulative changes in neurobehavioral measures of alertness as a function of sleep restriction were generally consistent. Subjective changes tended to precede performance changes by 1 day, but overall changes in both classes of measure were greatest during the first 2 days (P1, P2) and last 2 days (P6, P7) of sleep restriction. Data from subsets of subjects also showed: 1) that significant decreases in the MSLT occurred during sleep restriction, 2) that the elevated sleepiness and performance deficits continued beyond day 7 of restriction, and 3) that recovery from these deficits appeared to require two full nights of sleep. The cumulative increase in performance lapses across days of sleep restriction correlated closely with MSLT results (r = -0.95) from an earlier comparable experiment by Carskadon and Dement (1). These findings suggest that cumulative nocturnal sleep debt had a dynamic and escalating analog in cumulative daytime sleepiness and that asymptotic or steady-state sleepiness was not achieved in response to sleep restriction.

Night-to-night variability in CPAP use over the first three months of treatment.

The purpose of this study was to examine the relationship between night-to-night variability and nightly duration of continuous positive airway pressure (CPAP) therapy over the first 9 weeks of treatment and to determine when patients begin to establish a nonadherent pattern of use. Data were analyzed from a study of daily CPAP use covertly monitored in 32 diagnosed patients with obstructive sleep apnea (OSA) using a microprocessor monitor encased in a CPAP machine. Patterns of CPAP use were bimodal, based on the frequency of nightly use. Approximately half the subjects were consistent users of CPAP, applying it > 90% of the nights for an average of 6.22 +/- 1.21 hours per night, while the other half comprised intermittent users who had a wide range of daily use averaging 3.45 +/- 1.94 hours per night on the nights CPAP was used. The percent of days skipped was significantly correlated with decreased nightly duration (rho = -0.73, p < 0.0001). Analysis of the night-to-night pattern of use revealed that the two groups differed significantly in the nightly duration of CPAP use by the fourth day of treatment (p = 0.001). Exploration of factors that potentially differentiate the two groups revealed no reliable predictors. However, intermittent users continued to report significantly greater OSA symptoms (snoring, snorting, and apnea) posttreatment, suggesting that they continued to experience sleep disordered breathing.

An instrument to measure functional status outcomes for disorders of excessive sleepiness.

This article reports the development of the functional outcomes of sleep questionnaire (FOSQ). This is the first self-report measure designed to assess the impact of disorders of excessive sleepiness (DOES) on multiple activities of everyday living. Three samples were used in the development and psychometric analyses of the FOSQ: Sample 1 (n = 153) consisted of individuals seeking medical attention for a sleep problem and persons of similar age and gender having no sleep disorder; samples 2 (n = 24) and 3 (n = 51) were composed of patients from two medical centers diagnosed with obstructive sleep apnea (OSA). Factor analysis of the FOSQ yielded five factors: activity level, vigilance, intimacy and sexual relationships, general productivity, and social outcome. Internal reliability was excellent for both the subscales (alpha = 0.86 to alpha = 0.91) and the total scale (alpha = 0.95). Test-retest reliability of the FOSQ yielded coefficients ranging from r = 0.81 to r = 0.90 for the five subscales and r = 0.90 for the total measure. The FOSQ successfully discriminated between normal subjects and those seeking medical attention for a sleep problem (T157 = -5.88, p = 0.0001). This psychometric evaluation of the FOSQ demonstrated parameters acceptable for its application in research and in clinical practice to measure functional status outcomes for persons with DOES. Thus, the FOSQ can be used to determine how disorders of excessive sleepiness affect patients' abilities to conduct normal activities and the extent to which these abilities are improved by effective treatment of DOES.