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We reviewed current definitions of vigilance to propose a definition, applicable in sleep medicine. As previous definitions contained terms such as attention, alertness, and arousal, we addressed these concepts too. We defined alertness as a quantitative measure of the mind state governing sensitivity to stimuli. Arousal comprises a stimulus-induced upward change in alertness, irrespective of the subsequent duration of the increased level of alertness. Vigilance is defined as the capability to be sensitive to potential changes in one's environment, ie the capability to reach a level of alertness above a threshold for a certain period of time rather than the state of alertness itself. It has quantitative and temporal dimensions. Attention adds direction towards a stimulus to alertness, requiring cognitive control: it involves being prepared to process stimuli coming from an expected direction. Sustained attention corresponds to a state in which some level of attention is purposefully maintained, adding a time factor to the definition of attention. Vigilance differs from sustained attention in that the latter in addition implies a direction to which attention is cognitively directed as well as a specification of duration. Attempts to measure vigilance, however, are often in fact measurements of sustained attention., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

This two-centre observational study of vigilance measurements assessed the feasibility of vigilance measurements on multiple days using the Sustained Attention to Response Task and the Psychomotor Vigilance Test with portable task equipment, and subsequently assessed the effect of sodium oxybate treatment on vigilance in patients with narcolepsy. Twenty-six patients with narcolepsy and 15 healthy controls were included. The study comprised two in-laboratory days for the Maintenance of Wakefulness Test and the Oxford Sleep Resistance test, followed by 7-day portable vigilance battery measurements. This procedure was repeated for patients with narcolepsy after at least 3 months of stable treatment with sodium oxybate. Patients with narcolepsy had a higher Sustained Attention to Response Task error count, lower Psychomotor Vigilance Test reciprocal reaction time, higher Oxford Sleep Resistance test omission error count adjusted for test duration (Oxford Sleep Resistance testOMIS / MIN ), and lower Oxford Sleep Resistance test and Maintenance of Wakefulness Test sleep latency compared with controls (all P < 0.01). Treatment with sodium oxybate was associated with a longer Maintenance of Wakefulness Test sleep latency (P < 0.01), lower Oxford Sleep Resistance testOMIS / MIN (P = 0.01) and a lower Sustained Attention to Response Task error count (P = 0.01) in patients with narcolepsy, but not with absolute changes in Oxford Sleep Resistance test sleep latency or Psychomotor Vigilance Test reciprocal reaction time. It was concluded that portable measurements of sustained attention as well as in-laboratory Oxford Sleep Resistance test and Maintenance of Wakefulness Test measurements revealed worse performance for narcoleptic patients compared with controls, and that sodium oxybate was associated with an improvement of sustained attention and a better resistance to sleep., (© 2016 European Sleep Research Society.)

The regulation of sleep and wakefulness is well modeled with two underlying processes: a circadian and a homeostatic one. So far, the parameters and mechanisms of additional sleep-permissive and wake-promoting conditions have been largely overlooked. The present overview focuses on one of these conditions: the effect of skin temperature on the onset and maintenance of sleep, and alertness. Skin temperature is quite well suited to provide the brain with information on sleep-permissive and wake-promoting conditions because it changes with most if not all of them. Skin temperature changes with environmental heat and cold, but also with posture, environmental light, danger, nutritional status, pain, and stress. Its effect on the brain may thus moderate the efficacy by which the clock and homeostat manage to initiate or maintain sleep or wakefulness. The review provides a brief overview of the neuroanatomical pathways and physiological mechanisms by which skin temperature can affect the regulation of sleep and vigilance. In addition, current pitfalls and possibilities of practical applications for sleep enhancement are discussed, including the recent finding of impaired thermal comfort perception in insomniacs.

Context: Impaired vigilance and sleepiness are two majordaily complaints of patients with narcolepsy. We previously showed their sleepiness to be correlated to an abnormally regulated skin temperature, i.e., increased distal skin temperature compared with proximal skin temperature., Objective: Our goal was to investigate a possible causal contribution of skin temperature disturbances to impairments in the ability to maintain vigilance and wakefulness in narcolepsy., Design: In a modified constant routine protocol, the Psychomotor Vigilance Task (PVT) and the Maintenance of Wakefulness Test (MWT) were repeatedly assessed. Meanwhile, skin and core body temperatures were mildly manipulated within the thermoneutral range of the normal diurnal rhythm using a thermosuit and hot or cold food and drinks., Setting: Tertiary narcolepsy referral center in a university hospital, Patients or Other Participants: Eight patients (5 males) diagnosed with narcolepsy with cataplexy according to the ICSD-2 criteria (mean age +/- SD: 28.6 +/- 6.4, range 18-35 years)., Intervention(s): None., Main Outcome Measure(s): MWT sleep latency and PVT response speed., Results: Compared to core cooling, core warming attenuated the typical decline in PVT response speed with increasing time-on-task by 25% (P = 0.02). Compared to distal skin warming, distal skin cooling increased the time that the patients were able to maintain wakefulness by 24% (distal warming: 1.88 min. vs. distal warming: 2.34 min.; P < 0.01)., Conclusions: Core body and skin temperatures causally affect vigilance and sleepiness in narcolepsy. This could lead to future practical applications.

Study Objective: The severity of narcolepsy is commonly measured with the Multiple Sleep Latency Test (MSLT), focusing on the tendency to fall asleep. A neglected but perhaps equally important complaint is impaired performance in the waking state. We evaluated the Sustained Attention to Response Task (SART) for the quantification of vigilance in narcolepsy., Design: The SART involves withholding key presses to 1 in 9 target stimuli. In the present study, it was administered prior to each of 5 MSLT sessions in a 1-day study. The Epworth Sleepiness Scale was administered to measure subjective sleepiness. SART and MSLT results (number of errors and sleep latency) were compared using Receiver Operator Curves, sensitivity, and specificity., Setting: Tertiary narcolepsy referral center in a university hospital., Patients: Fifteen untreated narcoleptics and 15 matched controls., Interventions: None., Measurements and Results: The area under the receiver operating curve was 0.97 for the MSLT and 0.95 for the SART. Sensitivity and specificity for the MLST were 80% and 100% using a cutoff point of 5 minutes. For the SART, these values were 87% and 100%, using a 5-error cutoff. The SART and MSLT showed no correlation with each other or with the Epworth Sleepiness Scale., Conclusions: The SART, measuring attention, was abnormal as often as the MSLT, measuring sleepiness. The inability to remain vigilant during the day may be the most serious complaint in narcolepsy, since it impairs performance. The SART is valid in this respect, is easy to administer, and takes little time.

Besides excessive daytime sleepiness, disturbed nocturnal sleep is a major complaint of patients with narcolepsy. Previously, alterations in skin temperature regulation in narcoleptic patients have been shown to be related to increased sleepiness. This study tests the hypothesis that direct control of nocturnal skin temperature might be applied to improve the disturbed sleep of narcoleptic patients. Participants were eight patients (five males) diagnosed as having narcolepsy with cataplexy according to the ICSD-2 criteria, mean (SD) age 28.6 (6.4) years, range 18-35 years. During two nights, sleep was recorded polysomnographically while proximal and distal skin temperature were manipulated using a comfortable thermosuit that induced skin temperature to cycle slowly with an amplitude of only 0.4°C within the comfortable range normally observed during sleep. Logistic regression was used to evaluate the effect of skin temperature manipulation on the probability of occurrence of different sleep stages and nocturnal wakefulness. Proximal skin warming significantly suppressed wakefulness and enhanced slow wave sleep (SWS). In contrast, distal skin warming enhanced wakefulness and stage 1 sleep at the cost of SWS and REM sleep. The optimal combination of proximal skin warming and distal skin cooling led to a 160% increase in SWS, a 50% increase in REM sleep and a 68% decrease in wakefulness, compared with the least beneficial combi- nation of proximal skin cooling and distal skin warming. Subtle skin temperature manipulations under controlled conditions significantly improved the typical nocturnal sleep problems in narcolepsy. [ABSTRACT FROM AUTHOR]

Introduction: This study was designed to investigate the effect of Sodium Oxybate (SXB) treatment on vigilance in narcoleptics, by in-laboratory measurements as well as measurements in daily life with portable task equipment. Materials and methods: This two-centre observational study comprised a nine-day protocol, in which two days of in-laboratory vigilance measurements were followed by seven days of portable digital assistant (PDA) task battery administrations. Narcoleptic patients followed this procedure before and three months after stable treatment with the normal therapeutic dose of SXB (4.5–9.0g/day). In-laboratory measurements included the Maintenance of Wakefulness Test (MWT) and the Oxford Sleep Resistance (OSLER) test, a behavioural MWT. The MWT and OSLER test consisted both of four 40-min sessions in a quiet and dimly lit room. During the OSLER test, subjects were instructed to keep their finger in contact with a button which was placed in their lap, and to remove the finger for 1s when a red light-emitting diode (LED) flashed four feet away at eye level in the frontal visual field. The OSLER test was terminated when sleep-onset occurred or after 40min of being awake. Outcome measures of the OSLER were average sleep latency, the total omission error count (number of times the finger was not removed upon a flash) and the omission error count per minute duration of the test (OSLEROMIS/MIN). In-field testing comprised a 15-minute task battery consisting of a session of the Sustained Attention to Response Task (SART) and a session of the Psychomotor Vigilance Test (PVT) in random order, as well as the administration of the Stanford Sleepiness Scale. The task battery was administered on a pocket-size personal digital assistant (PDA) computer and had to be performed three times per day during 1-hour-intervals around 10:00h, 14:00h and 20:00h for seven days. The SART error count and PVT reciprocal average reaction time (1/RT) were considered the main outcome measures. Since the PVT and OSLER test had not yet been described in narcoleptics, and the use of a portable device in this study population was also new, a control group was included to compare baseline measurements of vigilance and sleep resistance with, in order to assess feasibility and validity of these measures. Data were analyzed by means of linear mixed effect models (LMMs) adjusted for age, time of day and centre. Results: In total, data from 26 narcoleptics (14 had post-treatment data available) and 16 controls were available for analysis. Data are presented as geometrical means with P values originating from the LMM analyses described above. Narcoleptics had a higher SART error count compared to controls (17.5 versus 10.4 errors), lower PVT 1/RT (0.32 versus 0.38ms-1), higher OSLEROMIS/MIN (4.9 versus 0.7 errors/minute), lower OSLER sleep latency (9.4 versus 36.4min), and lower MWT sleep latency (6.1 versus 33.4min), all P 0.01. Treatment with SXB was associated with a longer MWT sleep latency (9.2 versus 6.1min, P 0.01), lower OSLEROMIS/MIN (4.2 versus 4.9 errors/minute, P =0.01), and a slightly lower SART error count (17.1 versus 17.5 errors, P =0.02) in narcoleptics, but not with absolute changes in OSLER sleep latency or PVT reciprocal reaction time. Performance tended to decrease during the day for SART error count and OSLEROMIS/MIN after SXB treatment. Conclusion: PDA vigilance measurements are feasible and consistent with in-laboratory OSLER and MWT measurements in narcoleptics and controls. Sodium Oxybate was associated with a better resistance to sleep, measured by the OSLER and the MWT, and with a slight but significant improved vigilance, measured by the SART. This was mainly manifested in the morning. Acknowledgements: We thank our subjects for participating in this study; the sleep technologists from the University Hospital Zurich and the Leiden University Medical Centre for their help in data acquisition; and UCB for the financial support of this study. [Copyright &y& Elsevier]