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Biomedical subjects

T Akerstedt

Publications and source records attributed to T Akerstedt.

At least 19 recordsLinked to original sources
PubMed1992

Sleep on a shortening day/night schedule.

In 2 experiments subjects were exposed for 3.5 weeks to a gradually (0.2 h/day initially) shortening day/night cycle, ending at 22.8 h and 22.0 h, respectively. Shortening of the cycle led to an initial but temporary increase of sleep latency. When the reduction ceased at 22.8 h and this length was maintained, sleep parameters were not further affected and the temperature rhythm in most subjects remained entrained to the 22.8 h period, although some instability occurred towards the end. In the 22.0 h experiment the continued reduction beyond 22.8 h led to disturbed sleep on day 15, at a day length of 22.4 h. Total sleep time, stage 2 and sleep efficiency were then markedly reduced. At this point sleep coincided with the peak of the body temperature rhythm and the amplitude of the latter was extremely small. This was also the point when the body temperature rhythm 'broke out' from the sleep/wake rhythm and showed a large 6 h phase jump (delay). Towards the end of the experiment, when sleep was initiated in the circadian temperature trough, REM propensity was increased. It was concluded that several sleep parameters were affected by the reduction of the day/night cycle although the specific effects depended on the amount of phase advance and on whether desynchronization occurred. Within the range of entrainment, however, most sleep parameters were remarkably unperturbed by the considerable changes of circadian parameters.

Adult↗
PubMed1991

Hypnotics and sleep physiology: a consensus report. European Sleep Research Society, Committee on Hypnotics and Sleep Physiology.

The effects of hypnotics on descriptive and functional aspects of electrophysiological sleep parameters are assessed in this report. Because of the arbitrary definition of some of the criteria underlying the conventional sleep stage scoring procedure, computer-aided methods of EEG analysis have become increasingly important for recording and interpreting pharmacological effects on sleep. Of particular interest are the changes of EEG slow-wave activity, since this parameter varies as a function of prior sleep and waking. Several types of interaction between hypnotics and sleep regulation are discussed, some recent pharmacological developments are highlighted, and some common problems in clinical trials are specified.

Anti-Anxiety Agents↗
PubMed1991

Recovery within day-time sleep after slow wave sleep suppression.

Six subjects had their SWS activity suppressed by acoustic stimulation during a day-time (11.00 h) recovery sleep after a 4 h night sleep (03.00-07.00 h). Sleep was disturbed for a period corresponding to 90% of the duration of a preceding undisturbed baseline sleep (also at 11.00 h and preceded by a 4 h night sleep) and thereafter allowed to continue undisturbed until spontaneous awakening. The results showed that SWS and EEG power density were significantly reduced during suppression and that full recovery occurred before spontaneous awakening. The disturbed sleep was significantly longer than the baseline sleep. The increase in duration consisted mainly of SWS, stage 2 and REM. The results suggest that the suppression of SWS activity caused a need for an extension of sleep in order to allow recovery.

Adult↗
PubMed1991

Self-reported health and well-being amongst night security guards: a comparison with the working population.

The present study sought to relate the well-being of night workers to that of the working population in general. One hundred and ninety-seven male permanent night security guards were interviewed with regard to the occurrence of various symptoms during the previous 12-month period. The results were compared with the results from similar interviews with a representative national sample of males (n = 1769) in the Swedish workforce. An age standardized morbidity ratio was computed with control for various background variables. The results showed that the security guards had a 2-3 times higher occurrence of sleep disturbances and fatigue than the national sample. Among the variables not differing from the national sample were gastrointestinal problems, headache, nervous problems, depression, nausea, diarrhoea, and haemorrhoids. It was concluded that sleep/wake disturbances are considerably more usual in permanent night security guards than in the working population as a whole.

Adult↗
PubMed1991

Manifest sleepiness and the spectral content of the EEG during shift work.

Twenty-five three-shift workers in a process industry were subjected to ambulatory polysomnography during one afternoon and one night shift. The electroencephalographic (EEG) recordings were analyzed with spectral analysis. Subjective sleepiness increased during the night work but did not reach an extreme level. Five subjects fell asleep during night work and the involuntary naps were preceded by a few minutes of increased alpha (8-11.9 Hz) power density. Alpha and theta activity occurred in very short bursts. The hourly mean EEG alpha power density increased significantly but moderately during the night shift and correlated with subjective ratings of sleepiness. Theta power density (4-7.9 Hz) did not increase during the night shift, nor did it correlate with subjective sleepiness. It was suggested that the shift workers could prevent much of the polysomnographic manifestations of sleepiness by various types of activity (including succumbing to sleep). It was also suggested that averaging power density values across long time periods might not be an optimal strategy for detection of sleepiness, but rather some method of emphasizing the occurrence of alpha or theta bursts.

Adult↗
PubMed1991

Stability of day and night sleep--a two-year follow-up of EEG parameters in three-shift workers.

Twenty rotating three-shift workers participated. Night and day sleep in connection with work on afternoon and night shifts, respectively, were recorded using 24-hour polysomnographic recording techniques. The procedure was repeated 2 years later. Both day and night sleep showed high significant correlations between years for rapid eye movement (REM) sleep, slow wave sleep (SWS-stages 3 + 4), total sleep time, slow wave energy, in the delta band (obtained via spectral analysis) and subjective sleep quality. Stage 2, stage 1, percent waking, sleep latency, SWS latency and REM latency were not correlated across years. None of the variables showed a significant difference between years. It was concluded that core variables of sleep show considerable interindividual stability across time and that a 2-year exposure to rotating shift work does not affect sleep in experienced shift workers.

Adult↗
PubMed1991

Spectral analysis of sleep electroencephalography in rotating three-shift work.

Fourteen male rotating three-shift workers were subjected to 24-h ambulatory polysomnographic recording in connection with morning, afternoon, and night shift work (at home and at work). Total sleep time, stage 2, rapid-eye-movement sleep, and slow-wave sleep (stages 3 + 4) were significantly reduced during sleep in connection with the night and morning shifts. Other visually scored sleep parameters and slow-wave energy (spectral power density integrated across sleep) were not affected. The content of the sleep cycles did not differ between shifts. The sleep before the morning shift was characterized by subjectively increased difficulties of sleep initiation and sleep termination, as well as by insufficient recuperation. The night shift was characterized by increased subjective difficulties of maintaining sleep, but also by increased ease of sleep initiation. It was concluded that both morning and evening shifts interfered with sleep, although no effects of sleep deprivation were found.

Adult↗
PubMed1991

The dynamics of the first sleep cycle.

Eight subjects participated in an experiment in which sleep stages and electroencephalographic (EEG) power density during the first sleep cycles (and where such appeared, also second cycles) were studied in a design involving 8, 4, 2 or 0 hr of progressively postponed night-time sleep. Each of these four manipulations was followed by a day-time sleep beginning at 1100 hr. No significant changes in the duration of the first sleep cycle appeared. As the prior sleep loss increased both SWE (slow-wave energy; accumulated EEG delta power density) and SWA (slow-wave activity; EEG delta power per minute) increased during the 1100-hr sleeps. This was observed for the entire cycles, the nonrapid eye movement (NREM) periods, and the SWS periods, respectively. SWS latency decreased and SWS duration increased, respectively, markedly with prior waking. Also, for the progressively postponed sleeps (started at 2300 hr, 0300 hr, 0500 hr and 1100 hr) there were changes, but not as clear. After 28 hr of continuous waking there was a marked increase of SWA during SWS. Also, at this level there was a spill over of SWA to the second cycle. It is suggested that there might be a limit to the amount and intensity of SWS that can be accommodated in the first sleep cycle and that this limit is reached before the appearance of REM sleep.

Adult↗
PubMed1990

Physicians during and following night call duty--41 hour ambulatory recording of sleep.

Six house officers at two Stockholm hospitals were subjected to 41 h of continuous ambulatory recording of EEG and EOG in connection with night call duty, and to 24 h in connection with normal day work. The results showed that night call duty greatly interfered with sleep, reducing its duration to 4 h. The reduction mainly affected sleep stages 2 and REM. SWS was not affected, whereas EEG spectral power density in the 0.5-7.9 Hz band was suppressed. During subsequent time off, napping and night sleep increased total sleep length above baseline levels. It was concluded that night call duty of the present type causes considerable sleep loss.

Adult↗
PubMed1990

Subjective and objective sleepiness in the active individual.

Eight subjects were kept awake and active overnight in a sleep lab isolated from environmental time cues. Ambulatory EEG and EOG were continuously recorded and sleepiness ratings carried out every two hours as was a short EEG test session with eyes open for 5 min and closed for 2 min. The EEG was subjected to spectral analysis and the EOG was visually scored for slow rolling eye movements (SEM). Intrusions of SEM and of alpha and theta power density during waking, open-eyed activity strongly differentiated between high and low subjective sleepiness (the differentiation was poorer for closed eyes) and the mean intraindividual correlations between subjective and objective sleepiness were very high. Still, the covariation was curvilinear; physiological indices of sleepiness did not occur reliably until subjective perceptions fell between "sleepy" and "extremely sleepy-fighting sleep"; i.e. physiological changes due to sleepiness are not likely to occur until extreme sleepiness is encountered. The results support the notion that ambulatory EEG/EOG changes may be used to quantify sleepiness.

Adult↗
PubMed1990

Psychological and psychophysiological effects of shift work.

The psychophysiology of shift work is mainly related to circadian rhythmicity and sleep-wake phenomena. Individuals on a rotating three-shift or similar system work the night shift at the low phase of circadian rhythm. On retiring to bed in the morning they fall asleep rapidly but are prematurely awakened by their circadian rhythm and exhibit severe sleepiness and reduced performance capacity. In connection with the morning shift the circadian psychophysiology makes it difficult to fall asleep as early as needed during the preceding night. Around 0400 to 0500, when the individuals should rise, they have difficulties awakening because of the sleep loss and the circadian rhythm, which at that point is at its lowest. Subsequently, day work is characterized by sleepiness and reduced performance. It should be emphasized that it does not seem possible to improve one's ability to adjust over time, even with permanent night work. Older age and "morningness" personality are related to higher than average problems in adjusting.

Age Factors↗
PubMed1990

Behavioral and psychophysiological effects of the physical work environment. Research strategies and measurement methods.

An international course on the behavioral and psychophysiological effects of the physical work environment was held in Stockholm, Sweden, in April 1988 by the Nordic Institute of Advanced Training in Occupational Health and the Swedish National Institute of Occupational Health. It dealt primarily with the behavioral and psychophysiological responses to aspects of the physical work environment and was devoted to neural and behavioral functions. The increasing interest in these functions is mainly motivated by the involvement of the central nervous system in the adverse effects induced by unfavorable environmental conditions of the workplace and by the need for more sensitive indicators than those based solely on recognized occupational disease and pathology. By describing the main aspects of the research strategies and the measurement methods used in this field of research, this paper provides a background for the assessment and evaluation of the early behavioral and psychophysiological indices of potential occupational hazards.

Affect↗
PubMed1989

Catecholamine measurements in urine by high-performance liquid chromatography with amperometric detection--comparison with an autoanalyser fluorescence method.

In order to validate different methods of measuring urinary catecholamines (norepinephrine, epinephrine and dopamine) in humans, methods based on separation of catecholamines using reversed-phase or cation-exchange high-performance liquid chromatography with electrochemical detection were compared with an autoanalyser-based fluorescence method. Different methods for pre-chromatography sample purification were also studied. For measurements of urinary catecholamines, the reversed-phase-based chromatographic techniques studied were found to give less reliable results than cation-exchange chromatography, even if one of them (Clin Rep Urine Catecholamine Kit) gave almost as precise estimates. The autoanalyser technique yielded good results. It is concluded that cation-exchange chromatography with an appropriate sample work-up procedure (a combination of organic solvent extraction and alumina adsorption) is a reliable and accurate method for analyses of urinary catecholamines.

Acetates↗
PubMed1989

Sleep on the night shift: 24-hour EEG monitoring of spontaneous sleep/wake behavior.

The present study sought to objectively describe the spontaneous sleep/wakefulness pattern of shift workers during a 24-hour period. Portable Medilog tape-recorders were used for ambulatory EEG monitoring of 25 male papermill workers (25-55 years) during days with night and afternoon work. The results showed that sleep after night work was two hours shorter than after afternoon work. The sleep reduction affected mainly Stage 2 and REM sleep while slow wave sleep was unchanged. In connection with night work 28% of the workers took a nap in the afternoon. These naps contained a large proportion of slow wave sleep and were, apparently, caused by the sleep deficit after the short main sleep period. The EEG recordings also revealed that 20% of the participants had sleep episodes during night work. These naps were as long as the afternoon naps, were experienced as "dozing offs" rather than naps, occurred at the time of the trough of the circadian wakefulness rhythm, and were concomitant with extreme subjective sleepiness and low rated work load. It was concluded that not only the sleep of shift workers was disturbed, but also the wakefulness--to the extent that sleepiness during night work sometimes reached a level where reasonable wakefulness could not be maintained. The latter observation is probably of special importance in work situations demanding a great responsibility for human lives or for great economic values.

Adult↗
PubMed1988

Sleepiness as a consequence of shift work.

The results reviewed clearly demonstrate that shift work is associated with increased subjective, behavioral, and physiological sleepiness. Apparently, the effects are due to combined circadian and homeostatic (sleep loss) influences. Sleepiness is particularly pronounced during the night shift, and may terminate in actual incidents of falling asleep at work. In some occupations this clearly constitutes a hazard that may endanger human lives and have large economic consequences. These risks clearly involve a larger number of people and should be of great significance to society.

Arousal↗