The effects of chronic sleep reduction on the performance of cognitive tasks sensitive to sleep deprivation

Abstract

In four sleep loss experiments we aimed, first, to compare performance during long-term sleep reduction with performance during short-term total sleep deprivation, and second, to measure the effects of both methods of sleep loss on ability to ignore distracting irrelevant stimuli, using a hding embedded figures test (FEFT). Logical reasoning, auditory vigdance and finding embedded figures tasks were shown to be significantly sensitive to one night's sleep deprivation. However, in one sleep reduction study subjects reduced to a mean of 5.2 hours sleep per night for 4 weeks showed no performance deficits on logical reasoning. In a second sleep reduction study subjects reduced to a mean of 4.3 hours sleep per night for 4 nights, and subjects reduced to a mean of 5.3 hours sleep per night for 18 nights, showed no performance deficits on logical reasoning or auditory vigilance, despite their reports of severe increases in subjective sleepiness and reduced concentration. Both these sleep reduction groups, though, did show decrements on the FEFT, which we interpret in terms of dearousal increasing distractibility, which the sleep-reduced subjects could not overcome with effort, as they did with the other tests.A paradox within sleep loss research is that studies on subjects having one night's total sleep deprivation show deficits on certain tasks, some lasting for 10 min or less (Donnell, 1969;Glenville, Broughton, Wing, and Wilkinson, 1978;Wilkinson, 1961; Wimmer, Hoffmann, Bonato, and Moffitt, 1992), whereas long-term sleep reduction of a few hours per night is often found to result in no performance deficit (Horne, 1988a; Horne and Wilkinson, 1985).Single experiments usually look at just one of these methods of losing sleep. In this paper our first aim was to investigate groups of subjects under different conditions of sleep loss, but using the same tests, so that comparisons between the conditions could be made. Comparisons would be between different levels of sleep reduction, and between long-term reduction and short-term total sleep deprivation. This type of comparison had previously been performed over two nights by Wilkinson (1968), using six different levels of sleep length. He found that performance deficits result when subjects have 3 h sleep over one night, or 5 h sleep over two nights, which indicates that sleep loss can accumulate. He indicated, however, that as long as

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“…This pattern may be due to the early learning and interference trials being more influenced by attentional capacity (Blagrove, Alexander, & Horne, 1995), whereas later trials reflect longer-term memory capacities, which may be more stable. Further investigations to determine what other cognitive skills or non-cognitive variables (e.g., fatigue and caffeine use) may be impacting on early versus later learning trials of the BLT would be informative.…”

The effects of reversing sleep-wake cycles on sleep and fatigue on the crew of USS John C. Stennis

“…However, one group of subjects, whose sleep had been limited to 4.3 hours per night for 4 days, did perform worse on a task requiring focused attention, thereby suggesting they were more easily distracted (Blagrove, 1995). Caution should be used in accepting these results, however, as the performance tests were conducted only 3 to 6 times per week for 5 to 20 minutes at a time.…”

“…In contrast, Blagrove et al (1995) examined the effects of chronic sleep deprivation in 3 groups of young adults and noted no performance decrements in logical reasoning or auditory vigilance tasks, as compared to a control group. However, one group of subjects, whose sleep had been limited to 4.3 hours per night for 4 days, did perform worse on a task requiring focused attention, thereby suggesting they were more easily distracted (Blagrove, 1995).…”

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