Examination of the first-night effect during the sleep-onset period

Sleep. 2005 Feb;28(2):195-202. doi: 10.1093/sleep/28.2.195.


Study objectives: The present study examined the first-night effect during the sleep-onset period using the 9 electroencephalogram stage scoring system.

Design: After a week of monitoring sleep-wake habits with sleep diaries and wrist actigraphy, polysomnography recording was made for 3 consecutive nights.

Setting: Participants slept in their own private, individual, temperature-controlled bedroom in a sleep laboratory at the university.

Participants: 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.

Interventions: N/A.

Measurements and 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.

MeSH terms

  • Adult
  • Alpha Rhythm
  • Analysis of Variance
  • Electroencephalography
  • Female
  • Humans
  • Male
  • Polysomnography
  • Sleep Stages / physiology*
  • Theta Rhythm
  • Time Factors