6.5.2.4.3. Performance & mood: long-term effects 

6.5.2.4.3.1 Night time naps 
After 17 hours awake, a nap of one or two hours, from 9pm onwards, prevents physiological nocturnal reduction in mental performance.
This effect lasts for several hours after the end of the nap.
After sleep loss of two or three nights, the nap leads to an immediate and long-term negative effect on performance. This nap is very rich in deep slow-wave sleep.
 
 
 
 
 

6.5.2.4.3.2 Daytime naps 
A nap improves performance in memory and reaction time tasks requiring sustained attention.
It has a positive effect on subjective feeling: the subject is more relaxed and less anxious.
A nap of 30 minutes or 2 hours has the same positive effects.
Some will maintain that the improvement in performance is not related to the nap but rather to the circadian increase in performance during the day.
 
 

6.5.2.5. EFFICIENCY OF IN-FLIGHT NAPPING (NON-AUGMENTED CREW) 

One of the main recommendations promoted in these guidelines is based on the alternation of crew rest and activities, including cockpit napping. In fact, results obtained have shown that most 2-pilot crew tend to synchronize their activities along the flight. This was graphically highlighted by means of the ebb and flow fluctuations evidenced through the task analyses of flight logs performed by ET Systems (Speyer et al, 1999). That means they tend to be active at the same moment and consequently to be tired at the same moment. Therefore, it was suggested to desynchronize pilot activities through alternating passive and active flight monitoring to avoid simultaneous decreases of their alertness. In the case of extreme sleepiness, an appropriate napping strategy should be adopted by each of them. The efficiency of cockpit napping was first emphasized by Graeber et al (1990). Naps of around 20 minutes were taken during flight and planned in order not to hinder correct flight progress: they had to be taken until one hour before descent at the latest.
 
Main conclusions drawn from this study can be summarized as follows:
– pilots, while resting at their seats, can quickly obtain short sleep periods of good quality;

– naps increased performance as assessed by reaction time tests;

– pilots of the "nap" group had 5 times less drowsiness episodes than the control group, indicating the efficiency of these naps in maintaining alertness during flight, in particular during those phases that require high involvement. 

 
 
 
 
 
 
 
Nap efficiencies were also documented by LAA during the validation phase of its practical recommendations for alleviating in-flight alertness decrements. One of these recommendations consisted of proposing alternation of passive vigilance-active vigilance phases (refer to "monotony"). It was suggested that pilots take a short nap in their seats while in the passive vigilance stage, having formally informed the other active crewmember of their temporarily remote status. The active/passive alternation scheme stems from earlier work that clearly documents alertness decrements to sometimes occur for both pilots simultaneously. This appears to be mainly related to high sleep pressure, particularly during night flights.
　
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