Effects of an afternoon nap on nighttime alertness and performance in long-haul drivers

ArticleinAccident Analysis & Prevention 34(6):825-34 · December 2002with15 Reads
DOI: 10.1016/S0001-4575(01)00089-6 · Source: PubMed
Abstract
The effects of an afternoon nap on alertness and psychomotor performance were assessed during a simulated night shift. After a night of partial sleep restriction, eight professional long-haul drivers either slept (nap condition) or engaged in sedentary activities (no-nap condition) from 14:00 to 17:00 h. Alertness and performance testing sessions were conducted at 12:00 (pre-nap baseline), 24:00, 02:30, 05:00 and 07:30 h, and followed 2-h runs in a driving simulator. In the nap condition, the subjects showed lower subjective sleepiness and fatigue, as measured by visual analog scales, and faster reaction times and less variability on psychomotor performance tasks. Electrophysiological indices of arousal during the driving runs also reflected the beneficial effects of the afternoon nap, with lower spectral activity in the theta (4-7.75 Hz), alpha (8-11.75 Hz) and fast theta-slow alpha (6-9.75 Hz) frequency bands of the electroencephalogram, indicating higher arousal levels. Thus, a 3-h napping opportunity ending at 17:00 h improved significantly several indices of alertness and performance measured 7-14 h later.
    • "In spite of the insignificance of the basic index y, index (a+y)/b showed different statistical characteristics compared to index b/a due to the mutual addition effect of alpha waves and theta waves during the repetitive phase transition between wakefulness and microsleep. According to the EEG study of long distance driving done by Macchi et al. (2002), theta waves alone showed insignificant effect, but the index containing both theta and alpha band showed significant effect. There were significant differences between EEG indices before and after the accidents. "
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    • "Nap could function in managing sleep deprivation and arrhythmia (abnormal heartbeat) due to interfered circadian cycle (Verrier and Josephson 2009). The midday nap could function in recovering negative physical and psychological symptoms due to interfered night sleep (Bonnefond et al. 2001; Macchi et al. 2002) or narcolepsy (Takahashi 2003). It has been reported that 20%-40% of healthy adults are non-nappers (Pilcher et al. 2001). "
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    • "Several researchers indicated a relationship between cognitive task length and response time. Firstly, Levitt and Gutin (1971) found a non-monotonic effect on reaction time while Macchi et al. (2002) found a positive relationship between response time and cognitive task length; Furthermore, Boksem et al. (2005) found a mixed relationship based on post error responses which was negative and post correct responses which was positive after either a medium or longhaul physical task performance. "
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