Effects of an afternoon nap on nighttime alertness and performance in long-haul drivers.
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.
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ABSTRACT: Our aim was to investigate how circadian adaptation to night shift work affects psychomotor performance, sleep, subjective alertness and mood, melatonin levels, and heart rate variability (HRV). Fifteen healthy police officers on patrol working rotating shifts participated to a bright light intervention study with 2 participants studied under two conditions. The participants entered the laboratory for 48 h before and after a series of 7 consecutive night shifts in the field. The nighttime and daytime sleep periods were scheduled during the first and second laboratory visit, respectively. The subjects were considered "adapted" to night shifts if their peak salivary melatonin occurred during their daytime sleep period during the second visit. The sleep duration and quality were comparable between laboratory visits in the adapted group, whereas they were reduced during visit 2 in the non-adapted group. Reaction speed was higher at the end of the waking period during the second laboratory visit in the adapted compared to the non-adapted group. Sleep onset latency (SOL) and subjective mood levels were significantly reduced and the LF∶HF ratio during daytime sleep was significantly increased in the non-adapted group compared to the adapted group. Circadian adaptation to night shift work led to better performance, alertness and mood levels, longer daytime sleep, and lower sympathetic dominance during daytime sleep. These results suggest that the degree of circadian adaptation to night shift work is associated to different health indices. Longitudinal studies are required to investigate long-term clinical implications of circadian misalignment to atypical work schedules.PLoS ONE 07/2013; 8(7):e70813. · 3.53 Impact Factor
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ABSTRACT: 30 college students who have the habit of lunch time napping (LTN) participated in experiments under two different conditions: Having lunch time napping and not having lunch time napping. They were asked to complete three tasks in-cluding vigilance reaction, short-term memory, addition arithmetic; their performance was re-corded automatically by computer during 3 dif-ferent periods in the afternoon and early eve-ning. The analysis about the experimental data showed that: as for habitual nappers, midafter-noon nap zone existed, LTN played a very im-portant role in overcoming it, and did great help in enhancing their vigilance in the afternoon and early evening, however, LTN didn't bring sig-nificant positive effect to executing complex tasks (such as short-term memory and addition task) at the periods of time 16:30-17:30, 20:00-21:00. Finally, this article discussed the conclu-sions and its significance.
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ABSTRACT: Shift work is a reality in many sectors of industrial societies. Unfortunately, it is associated with several problems. Within this con- text, we highlight fatigue caused by extended working hours and the resulting increase in the risk of accidents. This is also a reality on Brazilian roads, with increasingly alarming rates of accidents involving intercity drivers. A significant number of such accidents is related to sleepiness caused by disruptions in the circadian rhythm. The necessity to drive for many consecutive hours without a pause, extended working hours, and mainly driving in the early hours of the morning may affect the driver's wakefulness state and performance. This may be due to a lack of synchrony with the temperature curve, as well as melatonin levels. To minimize the risk of accidents, work schedules should include regular pauses during the work journey. Moreover, such schedules should prevent professional drivers from working for more than 10 consecutive hours, as the risk of accidents increases significantly after the 8th hour at the wheel.