The lab is interested in the effects of sleep loss, sleep disturbance, sleep disorders, and sleep shifts on alertness and performance on a variety of tasks. One current emphasis is the causes insomnia (i.e., to what extent is insomnia a physiological problem such as central nervous system hyperarousal as opposed to a psychological problem such as anxiety or depression) and the consequences of insomnia (i.e., what is the impact of several nights of poor sleep on mood, alertness, and ability to work?). Another current emphasis is shift work. We are examining the ability to perform an assembly type task as a function of the length and timing of work shifts in a population of night shift workers.
You may request a full-text (paper in the mail) reprint by sending an email message to Dr. Michael Bonnet. Be sure to specify the document in which you are interested and a complete mailing address.
1. Bonnet, M.H. & Arand, D.L. Heart rate variability: Sleep stage, time of night, and arousal influences. Electroencephalography and Clinical Neurophysiology, 1996, in submission.
Spectral analysis was used to assess heart rate variability in consecutive 5-min epochs during the night in 12 normal adults. Simultaneous time coding of EEG and digitized EKG allowed examination of heart rate variability as a function of sleep stage, time of night and presence of EEG arousal. The results replicated previous studies in showing increases in high frequency components and decreases in low frequency components of heart rate variability across NREM sleep stages and opposite changes in REM sleep and wake. These results are consistent with sympathetic nervous system activation during REM sleep and wake periods. The shift in heart rate variability seen during REM sleep began in NREM sleep several minutes prior to standardly scored REM and often continued beyond the end of REM sleep. EEG arousals during stage 2 and to some extent REM sleep were also associated with changes in heart rate variability which were consistent with sympathetic activation. An examination of beat to beat intervals in proximity to EEG arousals showed heart rate acceleration at least 10 beats prior to the EEG arousal. The arousal data along with stage 2 sleep transition data support the contention that increases in central nervous system sympathetic activity precede and possibly play a role in the initiation of REM sleep and arousals during sleep.
Keywords: Sleep, sleep stages, heart rate, heart rate variability, spectral analysis
2. Bonnet, M.H. & Arand, D.L. The consequences of a week of insomnia. Sleep, 1996, in press.
A yoked control study used sleep recordings from 10 insomniacs to produce similar sleep patterns in a group of matched normal sleepers for seven nights to determine if specific EEG sleep patterns were responsible for the secondary insomnia symptoms reported by the insomniacs. Specifically, it has been found that insomniacs display increased tension/confusion, decreased vigor, personality disturbance, subjective overestimation of poor sleep, increased body temperature, increased 24-hour whole body metabolic rate, and increased MSLT values. Normal sleepers given the nocturnal EEG parameters of insomniacs displayed decreased tension, decreased vigor, decreased body temperature, and decreased MSLT values. The spectrum of changes seen in the normal sleepers given an insomniac sleep pattern was characteristic of mild partial sleep deprivation and not consistent with symptoms found in patients with primary insomnia. It was concluded that the secondary symptoms reported by patients with primary insomnia are probably not related to their poor sleep per se. Data from previous studies which varied physiological arousal were used to support the contention that the secondary symptoms of insomnia, including the poor sleep, occur secondary to central nervous system hyperarousal.
KEYWORDS: Sleep, Insomnia, Sleep Fragmentation, Sleep Deprivation, Partial Sleep Deprivation, Sleep Disorders, Metabolism.
3. Bonnet, M.H. & Arand, D.L. 24-Hour metabolic rate in insomniacs and matched normal sleepers. Sleep, 1995, 18, 581-588.
Groups of ten objectively defined insomniacs and age, sex, and weight- matched normal sleepers were evaluated on sleep, performance, mood, personality, and metabolic measures over a 36-hour sleep laboratory stay. Insomniacs were defined to have increased wake time during the night but also had decreased Stage 2 and REM sleep. As expected insomniacs reported increased confusion, tension, and depression and decreased vigor on the POMS mood scale throughout the evaluation period as compared to the normals. Insomniacs also had decreased memory ability on the short term memory test and the MAST. These performance and mood differences were not secondary to sleepiness, because the insomniacs also had significantly increased MSLT values throughout the evaluation period. In conjunction with the consistent mood, performance, and MSLT differences during the day and the sleep differences at night, whole body, measured at intervals across the day and throughout one night of sleep, was consistently elevated at all measurement points in the insomniacs as compared to the normals. The nocturnal increase in metabolic rate remained even after metabolic values from periods during the night containing wake time or arousals were eliminated from the data set. It was concluded that patients who report chronic insomnia may suffer from a more general disorder of hyperarousal (as measured here by a 24-hour increase in metabolic rate) that may be responsible for both the daytime symptoms and the nocturnal poor sleep. Future studies need to explore 24-hour insomnia treatment strategies which decrease hyperarousal.
KEYWORDS: Insomnia, metabolic rate, psychomotor performance, MSLT, mood, personality, sleep.
4. Bonnet, M.H. & Arand, D.L. Physiological activation in patients with sleep state misperception. Psychosomatic Medicine, 1996, In submission.
Objective: Sleep State Misperception insomnia has been commonly viewed as a perceptual or psychological problem. It was hypothesized that Sleep State Misperception insomnia like psychophysiological insomnia could be associated with increased physiological activation, here indexed by whole body metabolic rate.
Method: Groups of nine patients with Sleep State Misperception insomnia and age, sex, and weight-matched normal sleepers were evaluated on sleep, performance, mood, personality, and metabolic measures over a 36- hour sleep laboratory stay.
Results: Sleep State Misperception insomniacs had a subjective history of poor sleep and perceived their laboratory sleep as poor but had EEG parameters which did not differ statistically from matched normal controls. Sleep State Misperception insomniacs had abnormal MMPI values and were subjectively more confused, tense, depressed and angry than matched normals. These observations were similar in direction and magnitude to those seen in patients with psychophysiological insomnia. Sleep State Misperception insomniacs were also found to have significantly elevated 24-hour metabolic rate compared to matched normals.
Conclusions: The overall increase in whole body oxygen use was less than that seen in psychophysiological insomniacs but was consistent with the view that Sleep State Misperception insomnia may be a mild version or a precursor to psychophysiological insomnia.
KEYWORDS: Sleep State Misperception, insomnia, metabolic rate, psychomotor performance, MSLT, mood, personality, sleep disorders, sleep.
5. Bonnet, M.H. & Arand, D.L. Metabolic rate and the restorative function of sleep. Physiology and Behavior, 1996, 59, 777-782.
It has been shown that performance improves during sleep more rapidly after sleep deprivation than during normal sleep. Recovery after sleep deprivation is also characterized by a different sleep stage distribution and by a decreased metabolic rate compared to a normal night of sleep. The present study examined whether sleep during a period of increased metabolic rate was less restorative than a normal period of sleep. Twelve normal young adults participated for two 4-day periods. In each period, an undisturbed baseline sleep night was followed by baseline testing. On the subsequent night, Ss slept a total of 212 minutes starting at 0200 after consuming placebo or 400 mg of caffeine. After the nap, subjects remained awake for 41 hours until beginning an undisturbed night of recovery sleep. During the period of sleep loss, subjects remained at the sleep laboratory where they performed computer tests and MSLTs. The caffeine produced a significant increase in metabolic rate during the nap. Although total sleep time was held constant, there was an increase in stage 1 and a decrease in stage 4 sleep after caffeine use. Performance on addition and vigilance tasks was significantly decreased after the caffeine plus nap condition. However, no significant differences were found on the MSLT, and subjective vigor was significantly greater following the caffeine and nap combination. It was concluded that the beneficial effect of sleep in maintaining performance was decreased by increased physiological activation during sleep.
Keywords: Sleep Deprivation, Nap, Caffeine, Work Schedules, Continuous Performance
6. Bonnet, M.H. & Arand, D.L. Consolidated and distributed nap schedules and performance. Journal of Sleep Research, 1995, 4, 71-77.
This study compared alertness and psychomotor performance over an extended work period in which participants received either a 4-hour afternoon nap or four 1-hour naps during the night. It was hypothesized that alertness and performance would be superior during the night following the 4-hour afternoon nap and that overall level of performance would be related to the amount of sleep obtained. It was found that when a series of 1-hr naps were taken during the normal night period, oral temperature and psychomotor performance also declined. However, performance was relatively improved on the following evening. In contrast, with an effective 4-hr prophylactic nap, performance remained near baseline levels across the night. It was concluded that the placement of sleep periods during extended work be based on knowledge of when maximal performance would be required.
KEYWORDS: Shift Work, Sleep Deprivation, Nap, Prophylactic Nap, Performance
7. Bonnet, M.H. Gomez, S. Wirth, O. & Arand, D.L. The use of caffeine versus prophylactic naps in sustained performance. Sleep, 1995, 18, 97-104.
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 two nights and days of sleep loss. A total of 140 normal, young adult males participated at one of two study sites. 98 Ss at one site were randomly assigned to one of four nap conditions (0, 2, 4, or 8 hrs) and 42 Ss 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, Ss in the nap groups returned to bed at noon, 1600 hr, 1800 hr, or not at all. Bedtimes were varied so that all naps ended at 2000 hr. Ss in the caffeine groups received either a single 400 mg dose of caffeine at 0130 hr each night or repeated doses of 150 or 300 mg every six hours starting at 0130 hr on the first night of sleep loss. A placebo control group (no nap and placebo administered every six hours on the repeated caffeine schedule) was run at both sites. Ss remained awake and followed the same schedule of computer administered performance tests, mood scales, MSLT observations, and meals/breaks for 52 hours before being allowed a recovery night of sleep at their normal sleep time. Results are consistent with previous findings and suggest that performance, mood, and alertness are directly proportional to prophylactic nap length. Furthermore, an 8-hr nap is superior in maintaining performance, mood, and alertness to either single or repeated caffeine administrations. Naps, in general, provided longer and less graded changes in performance, mood, and alertness than did caffeine, which displayed peak effectiveness and loss of effect within about six hours. Shorter prophylactic naps and small repetitive doses of caffeine, however, did maintain performance, mood, and alertness during sleep loss significantly better than no naps or large single doses of caffeine. Neither nap nor caffeine conditions could preserve performance, mood, and alertness near baseline levels beyond 24-hours, after which levels approached those of placebo.
Keywords: Sleep Deprivation, Nap, Caffeine, Work Schedules, Continuous Performance, Prophylactic Sleep
8. Bonnet, M.H. & Arand, D.L. The impact of naps and caffeine on extended nocturnal performance. Physiology & Behavior, 1994, 56, 103-109.
It was hypothesized that alertness and performance during an extended work period would be improved by an afternoon nap and the subsequent use of caffeine during the night. Twelve young adults received a 4-hour afternoon nap and caffeine during the night during one session and four 1- hour naps during the night in a second session. After an afternoon nap, subjects had increased objective and subjective alertness, increased oral temperature and increased performance on complex tasks like logical reasoning and correct additions when compared to the condition which allowed four nighttime naps. It was concluded that the specific scheduling of a nap period in preparation for an all-night work shift where sleep would not be allowed could result in increased alertness and performance as well as a less conflicted work situation.
KEYWORDS: Shift Work, Sleep Deprivation, Nap Work Scheduling, Circadian Rhythm, Psychomotor Performance, Caffeine.
9. Bonnet, M.H. & Arand, D.L. Caffeine use as a model of acute and chronic insomnia. Sleep, 1992, 15, 526-536.
It was hypothesized that the metabolic effects of caffeine, which can be objectively measured, (i.e., physiological "arousal") could be used to develop a physiological arousal model of chronic insomnia in a group of normal young adults. Twelve normal young adult males participated for 11 nights after laboratory adaptation. Ss received caffeine 400 mg. TID for 7 nights and days. As predicted, the use of caffeine resulted in increased metabolic rate. Sleep efficiency was significantly reduced by caffeine and MSLT latencies were significantly increased. Some adaptation to the metabolic, sleep efficiency, and MSLT effects of caffeine was seen over the week of administration. Withdrawal effects (i.e., rebound sleep or sleepiness) were not seen for metabolic, MSLT or sleep variables. The data indicated that caffeine was effective in producing significant metabolic and sleep effects and that those effects were related. The results were consistent with the interpretation that a chronic decrease in sleep efficiency associated with increased physiological arousal, while producing subjective dysphoria, does not produce a physiological sleep debt.
KEYWORDS: Sleep, Insomnia, Caffeine, Sleep Deprivation, Sleep Disorders, Metabolism.
10. Bonnet, M.B., Berry, R.B., & Arand, D.L. Metabolism during normal sleep, fragmented sleep, and recovery sleep. Journal of Applied Physiology, 1991, 71, 1112-1118.
Average metabolic data were obtained for each three-minute period during consecutive nights of normal sleep, experimentally fragmented sleep, and recovery sleep in a group of 12 normal young adult males. Naturally occurring arousals and awakenings resulted in a characteristic increase in metabolism on the baseline night. The placement of brief, frequent experimental arousals on the following night resulted in significantly increased metabolism throughout the night and significantly decreased sleep restoration as measured by morning performance, mood, and alertness tests even though total sleep time was minimally reduced. Metabolic variables were significantly decreased as compared to baseline on the non-disturbed recovery night which followed the sleep fragmentation night. The data cannot be used to infer that increased metabolism during sleep causes non-restorative sleep, but the direction and time-course of metabolic change accompanying arousal are consistent with that hypothesis.
KEYWORDS: sleep; sleep fragmentation; sleep deprivation; sleep disorders; metabolic rate; metabolic changes.
11. Bonnet, M.H. & Arand, D.L. We are chronically sleep deprived. Sleep, 1995, 18, 908-911.
Data from recent laboratory studies indicate that nocturnal sleep periods reduced by as little as 1.3 to 1.5 hours for one night result in reduction of daytime alertness by as much as 32% as measured by the MSLT. Other data document that a) 17-57% of normal young adults have MSLT latencies of 5.5 min or less while 50% or fewer have MSLT values of 10 min or more; and b) 28-29% of young adults reported normally sleeping 6.5 hours or less on each week night. More extensive reduction of daily sleep amount is seen in night-shift workers. A minimum of 2-4% of middle age adults have hypersomnolence associated with sleep apnea. Together, these data show that significant sleep loss exists in 1/3 or more of normal adults, that the effects are large and replicable, and that similar effects can be produced in just one 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 6.5 hours or less 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.
Keywords: Sleep Deprivation, Sleepiness, Sleep Disorders, Work Schedule Tolerance.
12. Bonnet, M.H. & Arand, D.L. The chronic use of triazolam in older patients with periodic leg movements, fragmented sleep, and daytime sleepiness. Aging Clinical and Experimental Research, 1991, 3, 313-324.
Many studies have shown a relationship between fragmented nocturnal sleep and daytime sleepiness. In the current study, 9 patients, aged 55- 79, were identified with fragmented nocturnal sleep secondary to periodic leg movements and objective daytime sleepiness as verified by Multiple Sleep Latency Test. Patients had twelve weeks of treatment with 0.125 mg of triazolam following two screening nights and two placebo baseline nights. Two final placebo nights were placed five nights following the last medication night. The medication increased total sleep time and sleep efficiency throughout the administration period as compared to average placebo values. Total leg movements were not changed by triazolam. Generally, daytime performance, as measured by a vigilance task, and objective alertness, as measured by MSLT, were improved following the use of triazolam. No adverse reactions or significant side effects were noted. It was concluded that triazolam 0.125 mg, when used for up to 3 months, could improve sleep and daytime function in older patients with periodic leg movements, fragmented sleep, and daytime sleepiness.
Keywords: Periodic leg movements, nocturnal myoclonus, sleep disorders, aging, triazolam, benzodiazepine, excessive daytime sleepiness, sleep fragmentation.
13. Bonnet, M.H., Dexter, J.R. & Arand, D.L. The effect of triazolam on arousal and respiration in central sleep apnea patients. Sleep, 1990, 13, 31-41.
It was hypothesized that triazolam might decrease central apneas associated with arousal periods in patients with central sleep apnea by hastening the onset of consolidated sleep. Five male patients, diagnosed as having central sleep apnea on a screening night, participated in a double-blind randomized cross over study of the effect of placebo, 0.125 mg triazolam, and 0.25 mg triazolam on sleep, respiration, and daytime function. Results indicated that the medication increased total sleep and decreased central apnea index and number of brief arousals. Improved sleep quality was reflected in improved daytime psychomotor performance and alertness. These data, if replicated, imply that benzodiazepine use may be beneficial in patients with central sleep apnea.
Keywords: Central Sleep Apnea, Triazolam, Sleep Fragmentation, Sleep Disorders.
14. Bonnet, M.H. & Arand, D.L. The use of triazolam in older patients with periodic leg movements, fragmented sleep, and daytime sleepiness. Journal of Gerontology: Medical Sciences, 1990, 45, M139-M144.
Many studies have shown a relationship between fragmented nocturnal sleep and daytime sleepiness. In the current study, 11 patients, aged 55- 75, were identified with fragmented nocturnal sleep secondary to periodic leg movements and objective daytime sleepiness as verified by MSLT. In a double-blind, repeated measures, cross-over design, patients had three nights of treatment with placebo, 0.125 mg of triazolam, or 0.25 mg of triazolam following an adaptation night. The medication increased total sleep time and sleep efficiency while decreasing the number of stage changes although total leg movements were not changed. Generally, daytime performance and objective alertness were significantly improved following the use of triazolam. It was concluded that acute use of triazolam, particularly the 0.125 mg dose, could improve sleep and daytime function in older patients with periodic leg movements, fragmented sleep, and daytime sleepiness.
Keywords: Periodic leg movements, sleep disorders, triazolam, aging, benzodiazepine, excessive daytime sleepiness, sleep fragmentation.
15. Bonnet, M.H. The perception of sleep onset in normals and insomniacs. In R. Bootzin, J. Kihlstrom, & D. Schacter (Eds.) Sleep and Cognition. Washington, D.C.: American Psychological Association, 1990, 148-159.
Many means of measuring sleep onset have been described. Generally, physiological measures such as EEG, EMG, and auditory threshold agree that sleep onset occurs at the point of alpha drop. However, subjective reports of sleep onset almost never agree well with the physiological measures. In one study of normal young adults, it was found that sleep onset was perceived about four minutes after the appearance of the first sleep spindle. However, patients who report sleep onset insomnia invariably report taking much longer to fall asleep than their EEG findings indicate. In an initial study of sleep onset insomniacs, the insomniacs were found to overestimate their sleep onset latency whether their subjective estimates were made either on the following morning or at an awakening at the point of the first sleep spindle. A second experiment determined that the insomniacs do not simply misperceive all intervals of time. In fact, the only interval they misperceived was their nighttime sleep onset latency. A study currently in progress has used these findings to train sleep onset insomniacs to more correctly perceive their sleep onset by awakening them at discrete points during sleep and wake. Initial results indicate that the patients can learn to identify sleep and wake periods. After training the patients tend to have decreased overestimation of their sleep onset latency and feel that they will be significantly more likely to fall asleep within 30 minutes on a given night.
16. Bonnet, M.B. The effect of varying prophylactic naps on performance, alertness and mood throughout a 52-hour continuous operation. Sleep, 1991, 14, 307-315.
The current study reports the effect of 0 - 8-hr naps placed prior to two consecutive nights of total sleep deprivation. A total of 104 young adult male Ss were randomly assigned to one of four prophylactic nap conditions (0 hr, 2 hr, 4 hr or 8 hr). After a normal baseline night of sleep and a morning of baseline test performance, Ss returned to bed at noon, 4 PM, 6 PM, or not at all prior to a continuous operation which extended until each SŐs normal bedtime on the third following night. All Ss who napped arose at 8 PM, and all Ss maintained the same schedule of computer administered performance tests throughout the sleep loss period. Results indicated that performance and alertness in all nap conditions were improved in a dose-response fashion compared to a no-nap control throughout the first 24 hours of sleep loss. However, significant improvement in nap conditions compared to the no-nap condition was not seen in many variables during the second night of sleep loss. While an 8- hr nap prior to an operation maintained performance at a high level for 24-30 hours, significant improvement in alertness and performance as compared to the no-nap control was also documented by shorter naps. No nap could reverse the profound loss of alertness seen during the second night of sleep loss.
Keywords: sleep, sleep deprivation, continuous operations, prophylactic nap, psychomotor performance, work schedule tolerance
17. Bonnet, M.H. & Arand, D.L. The use of prophylactic naps and caffeine to maintain performance during a continuous operation. Ergonomics, 1994, 37, 1009-1020.
After a normal baseline night of sleep and a morning of baseline test performance, 24 young adult male Ss returned to bed from 1600 - 2000 prior to a 24-hour period of sleep loss. Twelve Ss received caffeine 200 mg at 0130 and 0730. Performance tests (correctly completed addition problems, vigilance sensitivity, and logical reasoning correct responses) all indicated maintenance of baseline performance levels in the caffeine group after administration of caffeine while performance declined in the placebo group. Similar results were found for the Multiple Sleep Latency Test and Oral Temperature, which both remained near baseline levels throughout the observation period in Ss receiving caffeine. The results indicated that the combination of a prophylactic nap and caffeine was more effective in maintaining nocturnal alertness and performance than was the nap alone. Of more interest was the fact that the group which was given the combination of nap and caffeine was able to maintain alertness and performance at very close to baseline levels throughout a 24-hour period without sleep.
Keywords: Sleep Deprivation, Nap, Caffeine, Continuous Performance, Prophylactic Sleep.
In laboratory opportunities (you need to be in the Dayton, Ohio area):
We are currently performing experiments to discover physiological differences between good sleepers and poor sleepers between the ages of 21 and 50. The experiments involve sleeping in the sleep laboratory at the Dayton Department of Veterans Affairs Medical Center for a few nights while we monitor your sleep. We will review your results with you, if you wish, and you will be paid for your participation in the study. If you have questions or would like more information, complete the REQUEST or give us a call at (513) 267-3910.
The Web presents a wonderful opportunity to collect systematic data (and an easy way to be overwhelmed by irrelevant information). We are currently thinking of ways to implement the former without achieving the latter. Your input would be appreciated.