Altered sleep/wake patterns and mental performance

doi:10.1016/j.physbeh.2006.09.007

Physiology & Behavior

Volume 90, Issues 2–3, 28 February 2007, Pages 209-218

https://doi.org/10.1016/j.physbeh.2006.09.007 Get rights and content

Abstract

Altered sleep/wake patterns involve, by definition, displaced sleep. The present review concludes that mental performance is strongly influenced by many forms of displaced sleep. Being exposed to the circadian low (during work/activity), extended time awake or reduced duration of sleep will impair performance. The effect is most pronounced in the laboratory setting, however, even if a number of studies have shown effects of for example night work on neuropsychological tests, and simulated work. In real shift work situations performance changes have been less pronounced. No studies have evaluated the effects on production, but accidents and serious mistakes have been clearly established in road transport and there seems to be clear effects also in health care. The effects are similar in connection with flights across several time zones (jet lag) but less data are available. It is suggested that there is a need for establishing the significance of impaired performance due to work hours in white collar and service work. Also the notion of individual differences in performance impairment is an important issue.

Introduction

Altered sleep–wake cycles in real life bring to mind mainly different types of night work or shift work, or related types like sea watches, as well as flights across time zones and perhaps disorders that affect the sleep/wake cycle. This will be the main focus of the present review. However, in order to understand how the effects are brought about, it is also necessary to study sleep–wake schedules in different laboratory situations, such as continuous wakefulness, simulated night work, living on an extended or shortened “day” (24-h period) or other manipulations of sleep timing. The existing material does not, however, suffice for a systematic review. The present approach will instead have a more narrative character, with the weaknesses in quality control that accompany such an approach.

The issue of altered sleep–wake patterns is important for several reasons. Apart from the obvious aspect that, in night work, sleep is displaced to the daytime and wakefulness to the night time, the displacement also changes the duration of wakefulness (increased or decreased depending on pattern) which for the average day worker would be 16 hours. It also changes the conditions for optimal sleep. These changes should affect sleepiness and performance and one would expect real-life situations to reflect this, as discussed below.

Section snippets

Different types of performance

One might also consider the definition of “mental performance”. Here the main focus will be on psychomotor performance, vigilance performance, and cognitive performance (memory, addition, logical reasoning). More complex decision-making (executive functioning) has not really been studied as a function of altered sleep–wake patterns other than as an effect of sleep loss. The latter type of cause will be discussed elsewhere in this issue.

It should also be pointed out that different types of

The key components in altered sleep/wake patterns

As indicated above, the effects of altered sleep/wake patterns depend on the circadian pattern of mental performance, the amount of sleep, the time awake, and the effects of displaced sleep on sleep duration. These components are briefly introduced below.

Effects on performance

Explaining the mechanism behind shift work problems was part of the rationale for many of the laboratory studies mentioned above (manned space flight was another). So simulations of shift work are a natural extension of the other laboratory studies, particularly since the real-life shift work situation is more difficult to control and to obtain usable data from.

A large number of such studies have been carried out either simulating night shift work or extending performance testing to the night

Interpolated tasks in real shift work settings

Most occupations lack measurable work performance measures. Thus, neuropsychological tests are used as proxies — interpolated performance measures. These are, of necessity, relatively short and simple in order to permit measures at work places. Thus, for example, reduced reaction time or poorer mental arithmetic have been demonstrated on the night shift [61], [62], [63]. Wojtczak-Jaroszova et al. [64] used manual dexterity and search performance and found worse performance on the night shift.

Performance and errors

As discussed in the introduction, one would expect negative effects on performance and safety at night. There have been, however, only few studies on performance in normal work situations. One of the classic reports in this area is by Bjerner et al. [91] who showed that errors in meter readings over a period of 20 years in a gas works had a pronounced peak on the night shift. There was also a secondary peak during the afternoon. Similarly, Brown [92] demonstrated that telephone operators

Additional shift work issues

Most of the impairment of performance in shift work is related to the night shifts. There are, however, several other issues that are of interest.

The nature and cause of the problem

One of the first reports of jet lag was that of Post and Gatty describing the out-of-phase problems during a flight across the globe [148]. Jet lag involves disturbed sleep, wakefulness and performance for some days after rapid transportation across several time zones [149]. Sleepiness seem to be the major component of jet lag, but also sleep, bowel movements, the need to urinate and other symptoms form part of the syndrome [137], [150], [151].

The reason for jet lag is that the biological clock

Individual differences and the measurement of performance and sleepiness

Most of the discussion on mental performance above has been based on neuropsychological tests or subjective ratings. There are at least two methodological aspects that need to be discussed in this context, perhaps especially in relation to field studies. This involves individual differences, context and validity of subjective sleepiness.

Conclusions

From the literature reviewed one may draw the conclusion that mental performance is affected by altered sleep/wake patterns and there are clear relations to serious mistakes and accidents. However, apart from road traffic and, perhaps, healthcare, we know very little about the consequences of altered sleep/wake patterns in terms of safety and production. Are decisions by factory workers, around-the-clock bankers, physicians, police officers, etc., worse during night shifts than they would be

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Altered sleep/wake patterns and mental performance

Abstract

Introduction

Section snippets

Different types of performance

The key components in altered sleep/wake patterns

Effects on performance

Interpolated tasks in real shift work settings

Performance and errors

Additional shift work issues

The nature and cause of the problem

Individual differences and the measurement of performance and sleepiness

Conclusions

Trends Neurosci

Organ Behav Hum Decis Process

Neurosci Lett

J Theor Biol

Neurosci Lett

Biol Psychol

Int J Ind Ergon

Ann Emerg Med

Ann Emerg Med

Electroencephalogr Clin Neurophysiol

Comparative utility of instruments for monitoring sleepiness-related performance decrements in the operational environment

J Sleep Res

Relative performance of college students as conditioned by time of day and day of week

J Exp Psychol

Studies on the physiology of sleep. VIII. Diurnal Variation in Performance

Am J Physiol

Circadian variations in choice reaction time

Z Exp Angew Psychol

The circadian system of man: Results of experiments under temporal isolation

Time of day effects on performance in a range of tasks

Psychon Sci

Circadian variations in performance, psychological ratings, catecholamine excretion, and diuresis during prolonged sleep deprivation

Int J Psychobiol

Impaired performance with acute sleep loss

Psychol Monogr

Some factors influencing the effect of environmental stressors upon performance

Psychol Bull

Impaired decision making following 49 h of sleep deprivation

J Sleep Res

Less effective executive functioning after one night's sleep deprivation

J Sleep Res

Prefrontal cortex: links between low frequency delta EEG in sleep and neuropsychological performance in healthy, older people

Psychophysiology

Phase shifts of human circadian rhythms due to shifts of artificial Zeitgebers

Chronobiologia

Partial adaptation to simulated time zone shifts

J Physiol (Lond)

Entrainment of human circadian rhythms by light–dark cycles

Photochem Photobiol

Bright light resets the human circadian pacemaker independent of the timing of the sleep–wake cycle

Science

Suppression of melatonin secretion in some blind patients by exposure to bright light

N Engl J Med

Spontanperiodik des Menschen bei Ausschlus aller Zeitgeber

Die Naturwissenschaften

Power density in theta/alpha frequencies of the waking EEG progressively increases during sustained wakefulness

Sleep

The circadian variation of experimentally displaced sleep

Sleep

Human sleep: its duration and organization depend on its circadian phase

Science

A dose–response study of sleep loss and spontaneous sleep termination

Psychophysiology

Performance following a night of reduced sleep

Psychon Sci

Dose–response relationship between sleep duration and human psychomotor vigilance and subjective alertness

Sleep

Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: a sleep dose–response study

J Sleep Res

The cumulative cost of additional wakefulness: dose–response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation

Sleep

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J Sleep Res