title: Examination of the first-night effect during the sleep-onset period.
abstract: OBJECTIVE
  The present study examined the first-night effect during the sleep-onset period using the 9 electroencephalogram stage scoring system.
  
  
  METHODS
  After a week of monitoring sleep-wake habits with sleep diaries and wrist actigraphy, polysomnography recording was made for 3 consecutive nights.
  
  
  METHODS
  Participants slept in their own private, individual, temperature-controlled bedroom in a sleep laboratory at the university.
  
  
  METHODS
  Eleven healthy student volunteers (5 women and 6 men, 21 to 25 years old, mean 22.7 years) who had no experience sleeping in a laboratory participated in the study.
  
  
  METHODS
  N/A.
  
  
  RESULTS
  The electroencephalogram during the sleep-onset period was scored manually for every 5-second epoch into 9 electroencephalogram stages. Latencies of the electroencephalogram stages were delayed on the first night, especially during the alpha-wave intermittent stages. The average time of the alpha-wave train, intermittent (> 50%) and the electroencephalogram flattening stage increased on Night 1. Stage changes among these stages also increased on Night 1. In contrast, stage changes between the alpha-wave intermittent stage (< 50%) and the theta-wave stage increased on Night 3.
  
  
  CONCLUSIONS
  Alpha-wave activity increased on Night 1, demonstrating that the activity of the wake-promoting system during the sleep-onset period was enhanced on the first night. From the second to the third night, the alpha-wave intermittent stage jumped to the theta-wave stage, omitting electroencephalogram flattening, suggesting that the electroencephalogram flattening stage is unlikely to appear during stable sleep-onset period. This is the first study to demonstrate the detail of the first-night effect during the sleep-onset period.
authors.affiliation: Graduate School of Biosphere Sciences, Hiroshima University, Higashi-Hiroshima, Japan.
authors.forename: Masako
authors.initials: M
authors.lastname: Tamaki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nittono
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Hayashi
authors.forename: Tadao
authors.initials: T
authors.lastname: Hori
mesh_terms: D000328:Adult; D000513:Alpha Rhythm; D000704:Analysis of Variance; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D017286:Polysomnography; D012894:Sleep Stages / Q000502:physiology*; D013826:Theta Rhythm; D013997:Time Factors