Sleep irregularity in the previous week influences the first-night effect in polysomnographic studies

Da Hye Lee, Chul Hyun Cho, Changsu Han, Ki Nam Bok, Jung Ho Moon, Eunil Lee, Heon Jeong Lee, Leen Kim

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


ObjectiveaaThe first-night effect is a well-known phenomenon resulting from an individual’s maladaptation to the unfamiliar environment of a sleep laboratory. However, there have been no direct reports of the effect of previous sleep patterns on the first-night effect. We aimed to investigate the effect the previous week’s sleep pattern on the first-night effect. MethodsaaTwenty-four young, healthy, male participants completed the study procedure. During one week prior to study, the participants kept sleep diaries and wore actigraphs to identify sleep-wake pattern. Two consecutive nights of polysomnography were conducted after that. Wilcoxon signed-rank tests were applied to compare sleep variables of the two nights. Variance (standard deviation) of sleep onset time during the previous week was used as an index of irregularity. A Kendall’s ranked correlation analysis and a linear regression test were applied to detect correlation between sleep irregularity and the first-night effect measured by polysomnography. ResultsaaThere were significant differences in the values of sleep efficiency (p=0.011) and wake after sleep onset (WASO) (p=0.006) between the two nights. Sleep efficiency was lower and WASO was higher on the first night as compared to the second night. Sleep irregularity in the previous week was negatively correlated with sleep efficiency (p<0.001) of the first night, but was not significantly correlated with any other sleep parameters. ConclusionaaWe replicated the existence of the first-night effect commonly observed in sleep studies. Sleep irregularity in the previous week may influence the first-night effect in polysomnographic studies.

Original languageEnglish
Pages (from-to)203-209
Number of pages7
JournalPsychiatry Investigation
Issue number2
Publication statusPublished - 2016 Mar


  • First-night effect
  • Polysomnography
  • Sleep efficiency
  • Sleep irregularity

ASJC Scopus subject areas

  • Psychiatry and Mental health
  • Biological Psychiatry


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