The effects of self-awakening on heart rate activity in a short afternoon nap

Objectives: This study examined whether anticipatory changes exist in heart rate prior to awakening from a nap by means of self-awakening. The effects of self-awakening on sleepiness after the short nap were also studied. Method: Nine students participated in 3 experimental conditions: (1) the control condition, in which participants watched television instead of taking a short nap; (2) the self-awakening condition, in which participants tried to wake up approximately 15 min after ‘lights off’ (criterion range: 15±5 min) and (3) the forced-awakening condition, in which participants were instructed to sleep for 30 min, but were awoken by the experimenter after 15 min. Results: In the self-awakening condition, heart rate gradually increased approximately 3 min before awakening. The error response ratio of the auditory-oddball task and the duration of doze time during the task were less after both types of nap conditions than in the control condition. Subjective sleepiness, which is measured after awakening, was lowest in the self-awakening condition. Conclusions: The results of this experiment suggest that self-awakening prepares autonomic activation that facilitates a more smooth transition from sleep to awakening, and reduces sleepiness after naps.