The Effects of Self-Awakening on Heart Rate Activity during a Short Afternoon Nap - Prof. , Apuntes de Psicología Fisiológica

¡Descarga The Effects of Self-Awakening on Heart Rate Activity during a Short Afternoon Nap - Prof. y más Apuntes en PDF de Psicología Fisiológica solo en Docsity! The effects of self-awakening on heart rate activity in a short afternoon nap Kosuke Kaida, Eriko Nakano, Hiroshi Nittono, Mitsuo Hayashi, Tadao Hori* Behavioral Sciences, Faculty of Integrated Arts and Sciences, Hiroshima University, Kagamiyama, 1-7-1 Higashi Hiroshima, Japan Accepted 11 May 2003 Abstract Objectives: This study examined whether anticipatory changes exist in heart rate prior to awakening from a nap by means of self- awakening. The effects of self-awakening on sleepiness after the short nap were also studied. Method: Nine students participated in 3 experimental conditions: (1) the control condition, in which participants watched television instead of taking a short nap; (2) the self-awakening condition, in which participants tried to wake up approximately 15 min after ‘lights off’ (criterion range: 15 ^ 5 min) and (3) the forced-awakening condition, in which participants were instructed to sleep for 30 min, but were awoken by the experimenter after 15 min. Results: In the self-awakening condition, heart rate gradually increased approximately 3 min before awakening. The error response ratio of the auditory-oddball task and the duration of doze time during the task were less after both types of nap conditions than in the control condition. Subjective sleepiness, which is measured after awakening, was lowest in the self-awakening condition. Conclusions: The results of this experiment suggest that self-awakening prepares autonomic activation that facilitates a more smooth transition from sleep to awakening, and reduces sleepiness after naps. q 2003 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved. Keywords: Sleepiness; Short nap; Heart rate activity; Self-awakening; Sleep inertia 1. Introduction It is well known that severe sleepiness often occurs in the afternoon (Broughton, 1989, 1998; Monk et al., 1996). This sleepiness is called ‘mid-afternoon dip’. High incidences of vehicle and work accidents occur in this mid-afternoon dip period (Mitler et al., 1988; Pack et al., 1995; Garbarino et al., 2001). Therefore, a prevention method is needed for the ‘mid-afternoon dip’. Some suggested methods have included taking caffeine, doing exercise, listening to the radio, increasing flowing cold air, etc. (Horne and Reyner, 1996; Reyner and Horne, 1998). Recently, the short nap (,30 min) method has attracted researchers’ attentions for prevention of ‘mid-afternoon dip’ (Hayashi et al., 1999a,b; Takahashi and Arito, 2000; Tamaki et al., 2000; Kaida et al., in press; Tietzel and Lack, 2001; Shirota et al., 2002). In our previous study, we examined how a person can comfortably wake up from a short nap (Kaida et al., in press). It was suggested that the self-awakening method was useful for avoiding sleep inertia, the strong sleepiness occurring immediately after waking (Kaida et al., in press). Some people have the ability to awaken at a designated time decided upon before sleeping (Moorcroft et al., 1997). This ability is called ‘self-awakening’ (Zepelin, 1986; Hawkins, 1989; Hawkins and Shaw, 1990; Moorcroft et al., 1997; Born et al., 1999; Matsuura et al., 2002a). On the other hand, the term ‘forced-awakening’ is used for awakening caused by external methods (e.g. an alarm clock, another person’s voice). Born et al. (1999) revealed that the intention of self-awakening increased plasma concen- trations of adrenocorticotrophin starting from 1 h before the awakening. This effect of self-awakening on plasma concentrations of adrenocorticotrophin can be interpreted as a preparation for awakening. With this preparation, self-awakening becomes more comfortable than forced- awakening. With respect to short naps, Kaida et al. (in press) revealed that subjective sleepiness was reduced and P300 amplitude remained at pre-nap levels after self-awakening, while a temporary drop in the P300 amplitude was observed immediately after forced-awakening. This result suggests Clinical Neurophysiology 114 (2003) 1896–1901 www.elsevier.com/locate/clinph 1388-2457/03/$30.00 q 2003 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved. doi:10.1016/S1388-2457(03)00167-6 * Corresponding author. Tel.: þ81-824-24-6580; fax: þ81-824-24-0759. E-mail address: tdhori@hiroshima-u.ac.jp (T. Hori). that the preparation effect for awakening might occur not only during night sleep, but also during afternoon naps. However,the study by Kaida et al. (in press) did not measure internal changes during short naps, but only revealed the effects of self-awakening on subjective and objective sleepiness after short naps. The adrenocortico- trophin Born et al. (1999) reported affects the autonomic nervous system indirectly through a chain of reactions. Considering this, self-awakening affects the activity of the autonomic nervous system and will cause an anticipatory activation before awakening from the daytime short nap as well as from nocturnal sleep. To reveal autonomic changes during a short nap, this experiment tested whether the existing anticipatory auto- nomic arousals (i.e. increasing heart rates and blood pressure) were observable. In addition to this, the effects of self-awakening on subjective sleepiness that remains during the post-nap period (i.e. sleep inertia) were also tested. The hypotheses of this study were that: (1) in the self- awakening condition, heart rate and blood pressure would gradually increase before awakening and (2) after self- awakening, subjective sleepiness and doze time during simple oddball tasks would be lower and shorter than after forced-awakening. 2. Participants and methods 2.1. Subjects Four males and 7 females participated in this study. Mean age was 21.7 ðSD ¼ 1:25Þ years. The calculations were performed on the data of 9 participants who succeeded in self-awakening (81.8%). Initial screening established good health, a regular sleep–awake pattern, the experience of self-awakening from nocturnal sleep, and the absence of daytime napping habits by all participants (3 males and 6 females, 21.6 years ðSD ¼ 1:24Þ). Total nocturnal sleep time of participants the night before the experiment day was 7.8 h ðSD ¼ 0:71Þ. All participants reported that they could self-awaken from nocturnal sleep. They agreed not to take caffeine or alcohol for 3 days before the experiment. All participants gave their written consent to participate. 2.2. Procedure Participants took part in 3 experimental conditions. Before the experiment, participants had taken a prepa- ration day in order to make laboratory adaptation. In this adaptation day, participants tried to self-awaken though the experimenter did not give feedback to participants whether it was successful. The experiment was carried out in a soundproof, temperature-controlled room. During the short nap, the intensity of illumination was diminished to 10 lx; this light level was called ‘lights off’. The experimental conditions were: (1) a control condi- tion, in which participants watched television in a supine position instead of taking a short nap; (2) a self-awakening condition, in which participants were instructed to awaken approximately 15 min after lights off began (criterion range: 15 ^ 5 min) and (3) a forced-awakening condition, in which participants intended to sleep for 30 min, but were awoken by the experimenter 15 min after lights off. The content of the television program without sound that participants saw in the control condition involved unre- markable landscapes. The order of each condition was counterbalanced between each participant (i.e. 5 partici- pants carried out the self-awakening condition first). In the self-awakening condition, participants signaled to the experimenter when they had awakened by pressing a small button switch. This action required slight movement of the right thumb. 2.3. Recording and data analysis Polysomnograph, heart rate and blood pressure were measured during the short nap. Electroencephalograms (EEG) from C3 and O1 were scored every 20 s according to the Rechtschaffen and Kales (1968) criteria and the Sleep Computing Committee of JSSR’s (2001) supplements and amendments criteria. Sleep stages were scored not only during a nap but also during the task. Total Stage 1 time was calculated in each task session. American Sleep Disorders Association (ASDA) arousals were defined according to the criteria of American Sleep Disorders Association (1992). In the ASDA criteria, ASDA arousal was defined as requiring at least 3 s duration of EEG frequency shift. Heart rate and blood pressure were measured using a Porta Press model 2 (TNO-TPF Biomedical Instrumenta- tion) on the left forefinger in the pre- and post-nap task sessions. During a nap, the measured finger was changed to the left middle finger for the comfort of participants. Variations of heart rate and blood pressure per 1 min in each participant were calculated as subtracted values from the values of the point at 10 min before the awakening. Six task sessions were carried out each day. The experi- mental schedule is shown in Fig. 1. The short nap started from 14:00 hours in every condition. The first session was performed before the nap or the rest period. The remaining 5 sessions, which involved the same task as the first session, were repeated after the nap or the rest period. One session (5 min) consisted of the auditory oddball task (4 min) and a short time interval in order to measure subjective sleepiness (1 min). Two pure tones, 1000 Hz (standard, frequency: 0.8) and 1050 Hz (target, frequency: 0.2), were used for the auditory oddball task. Participants were instructed to press the button with the right forefinger as soon as possible when they detected the target stimuli. The oddball paradigm (Polich and Kok, 1995) was made difficult for the sleepy participants in this study to recognize the difference between the two types of stimuli. The difference between K. Kaida et al. / Clinical Neurophysiology 114 (2003) 1896–1901 1897 at the fourth ðP , 0:05Þ and fifth sessions ðP , 0:01Þ. However, no significant difference was observed between the self-awakening and the forced-awakening conditions. 4. Discussion 4.1. Temporal behavior of heart rate during short naps Heart rates during short naps were monitored in this study. In the self-awakening condition, an anticipatory increase in the heart rate was observed, starting approxi- mately 3 min before awakening. This phenomenon can be interpreted as a preparation effect of self-awakening. In other words, this phenomenon might demonstrate that anticipatory autonomic activation prepares and facilitates a smooth transition from sleep to awakening. Our previous study (Kaida et al., in press) determined that self-awakening from a short nap reduced the sleep inertia just after the nap. The same was found in the current study. Autonomic activation before awakening very likely might be a cause of this reduction of sleep inertia. 4.2. Effect of self-awakening on sleep inertia Subjective sleepiness after a nap was lowest in the self- awakening condition. Error response ratio seems to be lower in the self-awakening condition than forced-awakening condition, though it was not significantly lower. These results support the attenuation effect of self-awakening on sleep inertia as reported in the previous study (Kaida et al., in press). 4.3. Effect of a short nap on afternoon sleepiness Since the present study was carried out during the ‘mid- afternoon dip’ period in a very boring situation, participants could not resist sleepiness during the monotonous task. They all became drowsy at least once in the post-nap/rest sessions. In the post-nap/rest periods, drowsy time during the task was longer in the control condition than it was in either of the nap conditions. Also, error (missing) response ratio fluctuated in relation to doze time. These results suggest that psychomotor errors are due to sleepiness (sleep Stage 1). If the sleepiness and errors occurred while driving or doing some high-risk work, serious accidents would be induced (Mitler et al., 1988; Pack et al., 1995; Garbarino et al., 2001). This study demonstrated that errors in a monotonous task condition could be reduced by a short nap as suggested by previous studies (Takahashi and Arito, 1998, 2000; Hayashi et al., 1999a,b). 4.4. Habituation effect of self-awakening Recently, Matsuura et al. (2002b) have reported the effects of self-awakening on nocturnal sleep structure. When self-awakening became habitual, sleep structure was not influenced by whether a person intends to self-awaken. In addition, people who self-awoke felt better in the morn- ing and had lower sleepiness in the afternoon compared with people who were awakened by forced-awakening. The above results suggest that the habit of self-awakening produces positive benefits. For short afternoon naps, this positive effect of self-awakening will be also studied. References American Sleep Disorders Association. EEG arousals: scoring rules and examples. Sleep 1992;15:173–84. Born J, Hansen K, Marshall L, Malle M, Fehm H. Timing the end of nocturnal sleep. Nature 1999;397:29–30. Broughton RJ. Chronobiological aspects and models of sleep and napping. In: Dinges DF, Broughton RJ, editors. Sleep and alertness: chrono- biological, behavioral, and medical aspects of napping. New York, NY: Raven Press; 1989. p. 71–98. Fig. 4. Error response ratio to the target stimuli in the oddball task ðn ¼ 9Þ. The term ‘Pre’ on the horizontal axis means the pre-nap/rest sessions. Fig. 5. Subjective sleepiness before and after the short nap/rest periods ðn ¼ 9Þ. The term ‘Pre’ on the horizontal axis means the pre-nap session. K. Kaida et al. / Clinical Neurophysiology 114 (2003) 1896–19011900 Broughton RJ. SCN controlled circadian arousal and the afternoon ‘nap zoon’. Sleep Res Online 1998;1:166–78. Garbarino S, Nobili L, Beelke M, De Carli Phy F, Ferrillo F. The contributing role of sleepiness in highway vehicle accidents. Sleep 2001;24:203–6. Hawkins J. Sleep disturbance in intentional self-awakening: behavior- genetic and transient factor. Percept Mot Skills 1989;69:507–10. Hawkins J, Shaw P. Sleep satisfaction and intentional self-awakening: an alternativeprotocol forself-reportdata.PerceptMotSkills1990;70:447–50. Hayashi M, Ito S, Hori T. The effects of a 20-min nap at noon on sleepiness, performance and EEG activity. Int J Psychophysiol 1999a;32:173–80. Hayashi M, Watanabe M, Hori T. The effects of a 20 min nap in the mid- afternoon on mood, performance and EEG activity. Clin Neurophysiol 1999b;110:272–9. Horne JA, Reyner LA. Counteracting driver sleepiness: effects of napping, caffeine and placebo. Psychophysiology 1996;22:81–7. Kaida K, Nittono H, Hayashi M, Hori T. Effects of self-awakening on sleep structure of a daytime short nap and on subsequent arousal levels. Percept Mot Skills, in press Matsuura N, Hayashi M, Hori T. Comparison of sleep/wake habits in university students with and without a habit of self-awakening. Psychiatry Clin Neurosci 2002a;56:223–4. Matsuura N, Hayashi M, Hori T. The effect of habitual self-awakening on sleep processes and subjective ratings of nocturnal sleep. Jpn J Physiol Psychol Psychophysiol 2002b;20:61–9. [in Japanese with English abstract]. Mitler MA, Carskadon MA, Czeisler CA, Dement WC, Dinges DF, Graeber RC. Catastrophes, sleep, and public policy: consensus report. Sleep 1988;11:100–9. Monk HT. A visual analog scale technique to measure global vigor and affect. Psychiatry Res 1989;27:89–99. Monk TH, Buyesse DJ, Reynolds CF, Kupfer DJ. Circadian determinants of the mid-afternoon dip in performance. Chronobiol Int 1996;13:123–33. Moorcroft WH, Kayser KH, Griggs AJ. Subjective and objective confirmation of the ability to self-awaken at a self-predetermined time without using external means. Sleep 1997;20:40–5. Ogilvie RD. The process of falling asleep. Sleep Med Rev 2001;5: 247–70. Pack IP, Pack AM, Rodgman E, Cucchiara A, Dinges DF, Schwab C. Characteristics of crashes attributed to the driver having fallen asleep. Accid Anal Prev 1995;6:769–75. Polich J, Kok A. Cognitive and biological determinants of P300: an integrative review. Biol Psychol 1995;41:103–41. Rechtschaffen A, Kales A. A manual of standardized terminology, techniques and scoring system for sleep stage of human subjects. Washington, DC: Public Health Service, US Government Printing Office; 1968. Reyner LA, Horne JA. Evaluation ‘in-car’ countermeasures to sleepiness: cold air and radio. Sleep 1998;21:46–50. Shirota A, Tanaka H, Nittono H, Hayashi M, Shirakawa S, Hori T. Volitional lifestyle in healthy elderly: its relevance to rest-activity cycle, nocturnal sleep, and daytime napping. Percept Mot Skills 2002; 95:101–8. Sleep Computing Committee of the Japanese Society of Sleep Research Society (JSSR), Hori T, Sugita Y, Koga E, Shirakawa S, Inoue K, Uchida S, et al. Proposed supplements and amendments to ‘a manual of standardized terminology, techniques and scoring system for sleep stages of human subjects’ the Rechtshaffen & Kales (1968) standard. Psychiatry Clin Neurosci 2001;55:305–10. Takahashi M, Arito H. Sleep inertia and autonomic effects on post-nap P300 event-related potential. Ind Health 1998;36:347–53. Takahashi M, Arito H. Maintenance of alertness and performance by a brief nap after lunch under prior sleep deficit. Sleep 2000;23:813–9. Tamaki M, Shirota A, Hayashi M, Hori T. Restorative effects of a short afternoon nap (,30 min) in the elderly on subjective mood, performance and EEG activity. Sleep Res Online 2000;3:131–9. Tietzel AJ, Lack LC. The short-term benefits of brief and long naps following nocturnal sleep restriction. Sleep 2001;24:293–300. Zepelin H. REM sleep and the timing of self-awakenings. Bull Psychon Soc 1986;24:254–6. K. Kaida et al. / Clinical Neurophysiology 114 (2003) 1896–1901 1901