High intention to fall asleep causes sleep fragmentation.

The aim of this study was to investigate the effects of intention to fall asleep on sleep quality in good sleepers using polysomnographic and subjective nap parameters. We hypothesized that high intention to sleep would lead to arousal, worsening sleep quality. A counterbalanced 2 × 2 experimental design with one intra-individual (neutral versus motivating instruction) and one inter-individual (instruction sequence) variable was used. Thirty-three good sleepers (22 females; mean age: 24.1 ± 8.4 years) each attended two 1-h daytime polysomnographic recording sessions in the laboratory. When providing motivating instruction, the experimenter insisted on the importance of falling asleep as quickly as possible and promised a financial reward. Compared with neutral instruction, motivating instruction was associated with increased waking after sleep onset, number of awakenings and arousal index during napping. No relationship between instruction and subjective nap appraisal was found. The effect of high intention on sleep fragmentation remained significant after controlling for habitual napping, depression, anxiety and sleepiness. Thus, our findings suggest that high intention to fall asleep worsened sleep quality, especially in terms of sleep fragmentation, in good sleepers.