The purpose of this study was to determine the relationship of subjective and objective sleepiness across several nights. Extreme groups were chosen based upon both Multiple Sleep Latency Test (MSLT) ...findings and report of characteristic subjective sleepiness, and groups were compared across sleep, demographic, performance, and physiologic variables.
Subjects spent 3 baseline nights and the following days in the laboratory. Standard polysomnographic recordings were made on each night. On each day, subjects had an MSLT, performance testing, and metabolic and heart rate observation periods.
Participants were 50 adult normal sleepers.
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Those subjects with sleep latencies on the MSLT of more than 10 minutes following the adaptation night (Alert) were compared with 2 groups of subjects with sleep latencies on the MSLT of less than 7 minutes following the adaptation night. Subjects with MSLT < 7 were divided into those who reported subjective sleepiness during the day (subjective sleepiness > 1 SD above the mean for the entire group-Sleepy-Sleepy) and those who did not report subjective sleepiness (subjective sleepiness < 1 SD above the mean for the entire group--Sleepy-Alert). The Alert group maintained longer sleep latencies than the other groups and had improved performance on vigilance compared to the Sleepy-Sleepy group on all days and on some days compared to the Sleepy-Alert group. Vigilance was improved in the Sleepy-Alert group compared with the Sleepy-Sleepy group on all days. The Alert group had higher heart rate and increased low/high spectral heart rate power compared to both sleepy groups, and the Sleepy-Alert group had higher heart rate and increased low/high spectral heart rate power compared to the Sleepy-Sleepy group at some points.
It was concluded that normal adults with short MSLT latencies differ from those with longer latencies on both cardiac and performance variables. Also, those individuals with short latencies can be divided into subgroups claiming subjective sleepiness or denying sleepiness. Those denying sleepiness have improved vigilance performance and greater heart rate and low/high spectral heart rate power compared to those with subjective sleepiness. Both the MSLT group differences and the subjective group differences imply that ability to maintain wakefulness and performance in sedentary situations may be related to innate ability to maintain physiologic arousal.
The Multiple Sleep Latency Test (MSLT) and Maintenance of Wakefulness Test (MWT) are standard clinical tests used to measure sleep tendency in clinical populations in which test results may lead to ...significant life change for patients. Loss of a driving license or drug seeking may provide significant motivation to patients to obtain needed results on these tests. In the current study, the effect of motivation on the ability to fall asleep or stay awake was examined.
Twelve subjects spent 3 nights and the following days in the laboratory. On the day following the first laboratory night (screen), subjects performed an MSLT and 40-minute MWT with normal test instructions. On the second or third day, subjects were randomly motivated to appear as sleepy as possible (ie, to fall asleep rapidly) on all of the tests. On the other day, subjects were motivated to be wakeful. The subject with the "best" performance in modifying their sleep latency was paid a bonus as the motivation.
For the MSLT, latency was significantly longer than baseline in the Wakeful condition. For the MWT, latency was significantly shorter in the Sleepy condition, as compared to baseline.
Subjects have the ability to increase but not decrease sleep latency on the MSLT, and this implies that the MSLT is a better measure of sleepiness rather than alertness. Subjects have the ability to decrease but not increase sleep latency on the MWT, and this implies that the MWT is a better measure of alertness, as compared with sleepiness.
Summary
The purpose of this study was to determine how long the effects of a brief period of physiological arousal persisted using repeated sleep latency testing and measurement of heart rate. ...Thirteen normal sleeping young adults spent two non‐consecutive nights and the following days in the laboratory. On each day, subjects had five sleep latency measurements – at 09:00, 09:30, 10:00, 10:30, and 11:00 hours. The 09:00 test was a premanipulation baseline. Following this nap, subjects either walked for 5 min (on one day) or rested in bed for 10 min (on another day) prior to the 09:30 hours sleep latency test. Significant increases in sleep latency were found at 09:30, 10:00, and 11:00 hours following the single 5‐min walk as compared with resting in bed (mean sleep latency after the walk was 11.7 min compared with 7.1 min for the resting condition). Heart rate was significantly higher throughout all of the postmanipulation naps following the walk. The elevated sleep latency is probably secondary to the changes in underlying physiological arousal as measured in this study by heart rate.
Data from recent laboratory studies indicate that nocturnal sleep periods reduced by as little as 1.3 to 1.5 hours for 1 night result in reduction of daytime alertness by as much as 32% as measured ...by the Multiple Sleep Latency Test (MSLT). Other data document that 1) 17%-57% of normal young adults have MSLT latencies of < or = 5.5 minutes, whereas < or = 50% have MSLT values of > or = 10 minutes and 2) 28%-29% of young adults reported normally sleeping < or = 6.5 hours on each weeknight. More extensive reduction of daily sleep amount is seen in nightshift workers. A minimum of 2%-4% of middle-aged adults have hypersomnolence associated with sleep apnea. Together, these data show that significant sleep loss exists in one-third or more of normal adults, that the effects are large and replicable and that similar effects can be produced in just 1 night in the laboratory. In light of the magnitude of this sleep debt, it is not surprising that fatigue is a factor in 57% of accidents leading to the death of a truck driver and in 10% of fatal car accidents and results in costs of up to 56 billion dollars per year. A recent sleep extension study suggests that the average underlying sleep tendency in young adults is about 8.5 hours per night. By comparison, the average reported sleep length of 7.2-7.4 hours is deficient, and common sleep lengths of < or = 6.5 hours can be disastrous. We must recognize the alertness function of sleep and the increasing consequences of sleepiness with the same vigor that we have come to recognize the societal impact of alcohol.
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Bonnet MH, Arand DL (Wright State University, Kettering Medical Center, and Wallace Kettering Neuroscience Institute, Dayton, OH, USA). Insomnia, metabolic rate and sleep restoration ...(Minisymposium). J Intern Med 2003; 254:–.
Studies have shown occasional evidence of increased physiological activity in patients with primary insomnia. We hypothesized that metabolic rate, as measured by overall oxygen use (), might be a more general index of increased physiological activity. An initial experiment found elevated both at night and during the day in patients with primary insomnia as compared with matched normal sleepers. A second experiment found significant but more modest increases in in patients with Sleep State Misperception Insomnia who complain of poor sleep but who had normal sleep by electroencephalographic (EEG) criteria. In a third experiment, normal young adults were given caffeine 400 mg three times per day (TID) for 1 week as a means of increasing and possibly producing other symptoms of insomnia. Participants developed many symptoms consistent with those seen in patients with primary insomnia (poor sleep, increased latency on the Multiple Sleep Latency Test, increasing fatigue despite physiological activation, and increased anxiety on the Minnesota Multiphasic Personality Inventory (MMPI)). In a final experiment, physiological arousal was again produced by caffeine to determine if sleep with elevated arousal would be less restorative. All subjects (Ss) slept for 3.5 h after being given 400 mg of caffeine. During 41 h of sleep deprivation that followed, there was no significant condition difference for the Multiple Sleep Latency Test or mood measures. The results provided only weak support for the idea that sleep is less restorative after physiological arousal.
Previous studies have shown that performance during sleep loss is improved by prophylactic naps as a function of varying nap length. Based on single-dose caffeine studies, a similar dose-response ...effect has been hypothesized on performance, alertness and mood during sleep loss. The present study compared the effects of repeated versus single-dose administration of caffeine and varying amounts of sleep taken prior to sleep loss on performance, mood and physiological measures during 2 nights and days of sleep loss. A total of 140 normal, young adult males participated at one of two study sites. Ninety-eight subjects at one site were randomly assigned to one of four nap conditions (0, 2, 4 or 8 hours) and 42 subjects at the second site were assigned to one of four caffeine conditions. After a normal baseline night of sleep and morning baseline tests of performance, mood and nap latency, subjects in the nap groups returned to bed at noon, 1600 hours, 1800 hours or not at all. Bedtimes were varied so that all naps ended at 2000 hours. Subjects in the caffeine groups received either a single 400-mg dose of caffeine at 0130 hours each night or repeated doses of 150 or 300 mg every 6 hours starting at 0130 hours on the 1st night of sleep loss. A placebo control group (no nap and placebo administered every 6 hours on the repeated caffeine schedule) was run at both sites.
Summary
The ability to maintain wakefulness under baseline and sleep deprivation conditions was examined in a group of 14 normal young adults. Subjects participated in both standard and manipulation ...Maintenance of Wakefulness tests after being awake for 7, 19, and 31 h. In the manipulation Maintenance of Wakefulness tests, subjects performed varying degrees of physical activity at the onset of stage 1 to allow them to preserve wakefulness. As expected, ability to maintain wakefulness declined as time awake increased. With amount of time awake held constant, wakefulness was enhanced most after standing and doing knee bends, less after standing, less after sitting up, and least after subjects were spoken to. The improvement in alertness after doing knee bends as compared to being spoken to was of the same relative magnitude as the decrease in alertness after one night of total sleep deprivation. As expected, heart rate also increased consistently as activity increased. Each subject had a negative correlation between their EEG sleep latencies and their minimum r‐r interval during the manipulation, i.e. the higher the heart rate, the longer the latency. These data were interpreted as a demonstration of the impact of discrete phasic arousal on the ability to maintain wakefulness.
Previous work has shown that background noise or music has a small positive impact on performance during sleep deprivation. The current study examined the effect of background music on the ability to ...fall asleep or remain awake. Twelve normal-sleeping young adults took multiple sleep latency tests (MSLT) and maintenance of wakefulness tests (MWT) after baseline sleep and one night of total sleep deprivation either with background music or under standard (quiet) conditions. It was hypothesized that the music would help maintain wakefulness both under baseline and sleep deprivation conditions. The results of the study showed that sleep latencies were increased in both MSLT and MWT when music was presented, but that this effect occurred primarily before subjects were sleep-deprived (a significant Music by Sleep Deprivation interaction). Sleep latencies were 15 and 11 min on the MSLT (33 and 26 min on the MWT) with Music as compared to Quiet after baseline sleep. Heart rate, used as a measure of physiological arousal, was significantly elevated in MWT and MSLT trials where music was presented. These data support previous work showing that level of arousal has an impact on measured sleep tendency which is independent of that of the sleep system. On a practical level, these data indicate that music may play a small beneficial role in helping to maintain arousal.
It has recently been shown that physiological arousal following walking increased sleep latencies during daytime naps as compared to sleep latencies following TV viewing. Patients with insomnia have ...been shown to have increased physiological arousal and to also have longer MSLT latencies. It was hypothesized that insomnia patients, who are at a higher state of physiological arousal, would be unable to relax while lying in bed and watching TV and therefore would have relatively longer sleep latencies in naps following TV watching (due to inability to relax) as compared to walking.
Twelve patients with psychophysiological insomnia took Multiple Sleep Latency Tests after either watching television for 15 minutes or after a 5-minute walk following baseline, sleep deprivation, and recovery sleep conditions.
Sleep Laboratory
Twelve patients with psychophysiological insomnia
Manipulation of state arousal and sleep deprivation
Sleep latencies were significantly longer following the walk as compared to watching TV (11.9 vs. 6.9 min. respectively). Sleep latencies were 13.4 and 3.8 min. following baseline and sleep deprivation conditions. Heart period, used as a measure of physiological arousal, was significantly elevated throughout naps following the walk as compared to naps following TV viewing. Heart period was also significantly correlated with nap sleep latency.
The insomnia patients in this study had significantly increased arousal, as measured by heart rate, and significantly longer sleep latencies after walking as compared to resting. The magnitude of these changes was similar to that seen in normal subjects in a previous study. These data, in concert with previous work, support the contention that measured sleep tendency is a combination of sleep drive and level of central nervous system arousal, where arousal has both state and trait components.
Eleven young adult subjects were briefly awakened after each minute of electroencephalographic-defined sleep for 2 consecutive nights after undisturbed laboratory adaptation and baseline nights. Two ...undisturbed recovery nights followed disruption nights. On disruption nights, subjects were awakened with an audiometer and signaled the awakening by subjective rating of sleep state or button push response. The disruption procedure resulted in severely fragmented sleep with only very small amounts of slow-wave and REM sleep. Total sleep time was reduced by approximately 1 h on each night. Arousal threshold increased 56 dB across the disruption nights. Following disruption, subjects performed more poorly and rated themselves sleepier than on baseline. The level of decline was similar to that seen after periods of total sleep loss of 40-64 h. Recovery sleep was also similar to that seen after total sleep loss. It was concluded that periodic disruption of sleep, perhaps by destroying sleep continuity, quickly results in impaired function. These data may help explain function loss in severe sleep apneics.
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