Objectives:
A short nap is a countermeasure against fatigue; however, the possibility of sleep inertia (SI) persists. Understanding its effects on piloting mental functions is crucial for the implementation of strategic naps.
Material and Methods:
Fifty well-slept healthy male volunteers, aged 24–45 years (mean ± standard deviation: 33 ± 5.5 years), participated in this study. Psychomotor aspects, executive control functions, and higher-order cognitive functions were studied. Psychometry was conducted using simple reaction time test (SRTT), Stroop test (ST), and digit symbol substitution test (DSST). An afternoon nap of 30-min served as the intervention. Pre-nap data were collected at 0800 h and at 1330 hours (h). After 1400 h, participants were allowed to sleep for 30-min. Data were collected for 2 h post-nap, every 15-min during the 1st h and every 30-min during the 2nd h.
Results:
SRTT response time was longer (p < 0.0001) in the post-nap period, and this effect persisted for 2-h. However, there was no post-nap change (p = 0.0527) in response accuracy. There was no significant change (p = 0.379) in the Stroop effect after the nap. The DSST, response time remained unchanged immediately post-nap (p = 0.367) but shortened and persisted after 30-min post-nap (p = 0.0088) for 2-h. The accuracy of responses in the DSST was unaffected.
Conclusion:
An afternoon nap of 30 minutes is sufficient to produce SI, thus impairing the motor speed. However, the accuracy of psychomotor and cognitive functions was unaffected. Meanwhile, the speed of higher-order cognitive functions was improved. Although the findings caution about the policy of using short naps as a countermeasure against fatigue in aviation, it is recommended to further validate the research after addressing the limitations mentioned in the study.