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1 UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP TITLE: Sleep Inertia and On-Call Readiness DISTRIBUTION: Approved for public release, distribution unlimited This paper is part of the following report: TITLE: Individual Differences in the Adaptability o Irregular Rest-Work Rhythms/Status of the Use of Drugs in Sleep-Wakefulness Management [les Differences entre individus concernant les facultes d' adaptation aux rythmes irreguliers activite-repos/le point sur l'utilisation des medicaments pour la gestion des periodes veille-sommeil] To order the complete compilation report, use: ADA The component part is provided here to allow users access to individually authored sections f proceedings, annals, symposia, ect. However, the component should be considered within he context of the overall compilation report and not as a stand-alone technical report. UNCLASSIFIED hfollowing comonent part numbers A 0compilation cnprie the ADP thru. ADP report-

2 14-1 SLEEP INERTIA AND ON-CALL READINESS Michele FERRARA 1, 2, Maria CASAGRANDE 1, 2, Silvio PORCU' 1, Luigi DE GENNARO 2 and Mario BERTINI 2 1 Aerospace Medicine Department, CSV, Pratica di Mare AFB, Pomezia 00040, Italy 2 Department of Psychology, University of Rome "La Sapienza", Rome 00185, Italy Introduction worse than before sleep. However, physiological phenomena are best described The effects of sleep deprivation and by sinusoidal rather than by square-wave chronobiological variations in performance functions (Bertini & Violani, 1992); are undoubtedly among the most pervasive consequently, the underlying behavioral limitors of human ability in all situations states cannot readily be switched on and off that require sustained periods of continuous at the transition to another state. For this performance and in around-the-clock work reason, if we consider the transition from settings (e.g. Dinges et al., 1988). These sleep to wakefulness as a complex process work scenarios are becoming increasingly that takes some time to be completed, more common, often involving highly skilled and than an exact shifting point from one state dedicated personnel as in sustained military of consciousness to another, sleep inertia operations, space flight preparation and simply becomes the cognitive-behavioral launching, crisis and catastrophe face of this transition process. management (Mitler et al., 1988). In all these situations, the negative effects of From a physiological point of view, sleep loss during sustained operations must during the awakening period a clear be compared to the adverse effects of sleep dissociation between different parameters is inertia upon abrupt awakening from sleep evident. Based on the standard EEG due to a possible emergency (Dinges et al., scoring system (Rechtschaffen & Kales, 1988; Dinges, 1990). 1968), the awake EEG is identified by a predominant alpha rhythm. Sleep inertia defines a period of transitory hypovigilance, confusion, However, the EEG represent only a disorientation of behavior and impaired fraction of all the state-determining factors. cognitive and behavioral performance that In other words, "the presence of all immediately follows awakening (Kleitman, 'polygraphic features of one state does not 1963). Sleep inertia is one of the most mean that no (unmonitored) variables of serious contraindications to the use of another state are present" (Mahowald & napping during quasi-continuous operations Schenck, 1992). As an example, Broughton if the individual may be required to perform (1968) showed that visual evoked complex tasks immediatly after sudden potentials (VEP) recorded upon awakening awakening at unpredictable times (Dinges et from slow-wave sleep (SWS) are more al., 1985). similar to those obtained during sleep than Physiological Substratum to baseline waking values. The author ascribes these results to an impairment of cerebral responsiveness ("functional Sleep inertia has been considered a deafferentation") after SWS awakenings. "paradoxical" phenomenon (Kleitman, Other indications of a slow shift from the 1963) since performance upon awakening is sleep EEG substrate to that of wakefulness Paper presented at the RTO HFM Workshop on "Individual Differences in the Adaptability to Irregular Rest-Work Rhythms/Status of the Use of Drugs in Sleep-Wakefulness Management", held in Venice, Italy, 3-4 June 1999, and published in RTO MP-31.

3 14-2 come from the study of the EEG power the most critical factors on sleep inertia spectra during spontaneous sleep-wake concerns its duration and time course. transitions (Ogilvie & Simons 1992). The FFT analyses of EEG sampled during However, although sleep inertia has been spontaneous arousals from sleep showed a incorporated in several models of sleep and non-predicted gradual and continued drop vigilance regulation (e.g., Achermann et al., of theta and delta power well into the first 1994; Akerstedt & Folkard, 1997; Folkard few minutes of wakefulness. There was a & Akerstedt, 1992), only a few attempts statistically significant difference between have been made to experimentally quantify sleeping and waking delta only after the its time course. Most authors have typically subject had behaviorally responded to three made only one performance assessment consecutive tones (i.e. about 70 sec after after awakening (e.g. Naitoh et al., 1993), the first response). not allowing the determination of the time course and duration of sleep inertia. Due to Similarly, recent studies on cerebral this methodological limitation, sleep inertia blood flow -CBF- (e.g., Meyer et al., 1987) has been generally reported to be shortand cerebral blood flow velocities -CBFV- lasting, being comprised between 1 and 20 during sleep (e.g., Hajak et al., 1994; minutes (Dinges et al., 1990; Hartmann & Kuboyama et al., 1997) as indirect but Langdon, 1965; Hartmann et al., 1965; reliable indexes of the underlying neuronal Langdon & Hartmann, 1961; Seminara & metabolism and activity (e.g., Sokoloff, Shavelson, 1969). 1981), also suggest that the periods immediatly following nocturnal and More recently, Achermann and comorning awakenings have blood flow workers (1995) addressed this issue by characteristics that are not comparable to assessing performance every 20 minutes (4 daytime levels. Moreover, Hajak and co- times) during the first hour after awakening workers showed that upon morriing from nighttime sleep or from an evening awakening, subjects required up to half an nap, and finally after three hours from each hour to reach CBFV values corresponding awakening. They found sleep inertia to to the waking state of the previous evening, subside according to an exponential The delayed increases in CBFV after function, and to persist for slightly less than awakening provide another example of one hour. On the other hand, Jewett and dissociation between different physiological coll. (1999) reported that subjective parameters of sleep-wake transition, further alertness and cognitive performance reach stressing the slowness of the sleep-wake the baseline waking values about 2 hours transition. after awakening; in this case, too, sleep inertia subsided according to an exponential Sleep Inertia and Sleep Management function. Finally, in an unpublished study from our laboratory (Ferrara et al., Clearly, sleep inertia has relevant unpublished) we found that cognitive operational implications. As already performance reaches the baseline level after mentioned in the Introduction, from a about 30 minutes from the morning sleep-logistic perspective, the main problem awakening, showing an increasing linear is to weigh the effects of sleep loss on trend during the first 75 minutes after sleepiness and performance against the awakening, while sensory-motor and motor adverse effects of sleep inertia upon abrupt performance was still below baseline levels awakening from sleep due to a possible in the same period of time. emergency. From this point of view, one of

4 Sleep Inertia: Modulating Factors temperature rhythm - are not consistent. Conflicting evidence comes from studies of Sleep inertia duration and magnitude can be napping with and without previous sleep modulated by several factors. There are deprivation (e.g., Bonnet & Arand, 1995; well-known differential effects of Tassi et al., 1992; Naitoh et al., 1993), as REMINREM sleep stages on performance well as from repeated awakenings during upon awakening. More specifically, SWS nocturnal sleep (e.g., Balkin & Badia, 1988; awakenings have greater negative effects on Rosa et al., 1983; Rosa & Bonnet, 1985). A subsequent performance than REM sleep more accurate description of circadian awakenings. These effects have been influences on sleep inertia needs the support demonstrated with a wide array of tasks: of further empirical data. simple motor tasks (Tebbs & Foulkes, 1966; Wilkinson & Stretton, 1971); Moreover, sleep inertia seems to sensory-motor tasks (Scott & Snyder, dramatically depend on the type of task 1968; Feltin & Broughton, 1968); and used, highly demanding cognitive and cognitive tasks (Scott & Snyder, 1968; attentional tasks being much more affected Stones, 1977). than simple motor ones (Muzet et al., 1995). At variance with physiological However, it has been claimed that sleep sleepiness, which in self-paced tasks affects structure is also very important in speed of performance more than accuracy, determining sleep inertia (Dinges, 1990). it has been claimed that sleep inertia exerts The profound modification in sleep a negative influence on both, but architecture and the increased sleep depth particularly on the latter (Balkin & Badia, caused by sleep deprivation dramatically 1988; Naitoh et al., 1993; Ferrara et al., exacerbate sleep inertia and cognitive unpublished b). impairment upon awakening from recovery sleep (Dinges et al., 1985). It has also been In conclusion, although it is often found that cognitive decrements after difficult to compare results of studies on abrupt awakenings from 1 and 2 hour naps sleep inertia, since several different show a linear relationship with SWS experimental designs and tasks have been amount during the nap (Dinges et al., 1981; used, a few clear indications seem to 1985). emerge. The intensity of sleep inertia is strongly influenced by some homeostatic Moreover, the negative influence of sleep variables linked to SWS amount and, sleep deprivation on sleep inertia seems to more generally, to depth of and pressure for interact with time-of-night or circadian sleep. Finally, circadian factors and factors in producing even more dramatic previous sleep loss exacerbate sleep inertia effects. As an example, Naitoh (1981) by adding their simple effects. reported that, after a 2-hour nap taken early in the morning ( ) following 45 Sleep Inertia: Possible Countermeasures hours of continuous work without sleep, both task performance and self rating of From a brief review of the literature on the mood, sleepiness and fatigue remain physiological basis and modulating factors deteriorated at the levels of those who of sleep inertia, we will try to extrapolate stayed awake. some countermeasures against the detrimental effects of sleep inertia on More generally, the outcomes performance upon awakening, to be applied concerning the modulation of sleep inertia when it is possible in operational settings. by circadian factors - mainly linked to body 14-3

5 14-4 The first countermeasure could be to et al., 1993). More recently, it has been reduce the probability of awakening out of reported that following the "normal SWS, since it is well known that SWS morning routine" (i.e., getting out of bed, awakenings yield the greatest performance taking a shower, having breakfast) does not decrements. One possibility is to allow abolish sleep inertia as compared to a sleep when the occurence of SWS is very constant routine in bed (Jewett et al., low (e.g., in the morning). Another strategy 1999). In the same experiment (Jewett et can be to allow naps of about al., 1999), it was found that exposure to minutes (i.e., the mean duration of a normal normal room light (about 150 lux) upon NREM-REM sleep cycle), minimizing the awakening did not improve performance as probability of a SWS awakening. Some compared to very dim light (about experimental data confirm the usefulness of lux). this strategy, by showing that sleep inertia magnitude after a 20-min and a 80-min nap Sleep Inertia: Open Questions are very similar, while the worst performance upon awakening is recorded Sleep inertia is still a poorly understood after a 50-min nap (Stampi, 1992). phenomenon: from the point of view of its Obviously, a 80-min nap should be physiological substratum, that could be preferred to a 20-min nap because of its approached in the near future with the greater restorative power. newest and more sophisticated neuroimaging techniques; as regards the Another very important strategy to sleep-related modulating factors and minimize sleep inertia is to avoid a long psychological and personality variables that period of wakefulness before allowing a may influence it. However, a few research nap, since the increase of sleep depth areas that should be explored to give caused by sleep deprivation dramatically important answers on sleep inertia to be exacerbates sleep inertia (Dinges et al., applied in operational fields will be pointed 1985). out: In addition, awakening near the The first unexplored topic is the role of circadian nadir of body temperature should individual differences in reactions to the also be avoided, especially if the sleep effects of sleep inertia. We all anecdotally period follows sleep deprivation (Naitoh, know that individuals show a wide range of 1981). variation with respect to their perceived It has been reported that washing one's ability to function immediately after awakening. However, the literature on face with cold water immediately after sleep inertia has definitely ignored this awakening is a simple but effective tool to problem, relegating individual differences fight sleep inertia (Labuc, 1978, 1979). to a role of "confusing variable" to be More generally, every "alerting" factor controlled. The study of individual (i.e., noise, light, physical exercise) should differences modulation of sleep inertia will be useful in counteracting sleep inertia, add very important knowledge to the even though - at present - only few definition of the psychophysiological profile attempts have been made to assess their of tolerance to irregular work hours. effectiveness. As an example, pink noise (75 dba) administered during the first hour The same applies to the role of after awakening improves response speed psychological factors, like motivation, in at 0500 but not at 0800, when it has the modulation of sleep inertia. One should detrimental effects on performance (Tassi believe that motivation can be a strong and

6 efficient countermeasure to sleep inertia for Achermann P, Werth E, Dijk DJ, Borbely A. a fighter pilot sleeping on-call, when he is (1995) Time course of sleep inertia after requested to be in the cockpit at nightime and daytime sleep episodes metres a.s.l. just 5 minutes after Archives Italiennes de Biologie, abrupt awakening. However, this topic 134: should be specifically evaluated. Akerstedt T, Folkard S. (1997) The threeprocess model of alertness and its For operational purposes, the duration extension to performance, sleep latency, and time course of sleep inertia after naps and sleep length. Chronobiology taken at different times of the day should International, 14: also be further assessed, since available Balkin, T.J., & Badia, P. (1988). data are inconclusive. Relationship between sleep inertia and sleepiness, cumulative effects of four It would be very important to have some nights of sleep disruption/ restriction on pharmacological countermeasures to sleep performance following abrupt nocturnal inertia, such as very fast acting stimulants, awakenings. Biological Psychology, 27, to be used in operational settings when the need for high levels of alertness and Bertini, M., & Violani, C. (1992). The Post performance immediately after awakening Awakening Technique in the should arise. To our best knowledge, the investigation of cognitive asymmetries use of stimulants to counteract sleep inertia during sleep. In The Neuropsychology of effects has never been tried, not even in Sleep and Dreaming, J. Antrobus & M. laboratory settings. Bertini (Eds.), L. Erlbaum Ass. Publ., Hillsdale, New Jersey. Non-pharmacological countermeasures Bonnet, M.H., & Arand, D.L. (1995). to sleep inertia could also be very useful, Consolidated and distributed nap particularly because pharmacological schedules and performance. Journal of measures are currently lacking. Generally Sleep Research, 4, speaking, any alerting factor could be Broughton, R. J. (1968) Sleep disorders, assessed to counteract sleep inertia: disorders of arousal? Science; 159, physical and/or mental exercise, external noise, bright light. As regards noise, Czeisler C., Johnson M., Duffy J., Brown although in at least one study pink noise E., Ronda J., Kronauer R. (1990). has been administered for one hour after Exposure to bright light and darkness to awakening with non-univocal results (Tassi treat physiologic maladaptation to night et al., 1993), the effectiveness of different work. New England Journal of types of noise with different intensities and Medicine, 322, durations should be assessed. Bright light Dinges DF, Orne MT, Orne EC. (1985) might also be effective against sleep inertia, Assessing performance upon abrupt since its alerting effects are well established awakening from naps during quasi- (e.g., Czeisler et al., 1990). continuous operations. Behav Res Meth Instr Comp, 17: References Dinges, D. F. (1990) Are you awake? Cognitive performance and reverie Achermann P, Borbely A. (1994) Simulation during the hypnopompic state. In: of daytime vigilance by the additive Bootzin, R., Kihlstrom, J., Schacter, D., interaction of a homeostatic and a eds. Sleep and Cognition. Washington circadian process. Biol Cybern, 71:115- D.C.: American Psychological 121. Association;

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