The first-night effect may last more than one night

Area of Science:

• Sleep science
• Neuroscience
• Psychiatry

Background:

• The first-night effect (FNE) in polysomnography is commonly believed to resolve after one night.
• However, some evidence suggests that certain sleep variables, particularly those related to rapid eye movement (REM) sleep, require more time to stabilize.
• Current practices often assume the second night of polysomnography is suitable for research and clinical use without limitations.

Purpose of the Study:

• To investigate the habituation dynamics of polysomnography under optimal conditions.
• To determine the duration required for sleep parameters to stabilize during polysomnography.
• To explore the implications of sleep adaptation on research and clinical interpretations.

Main Methods:

• Four consecutive nights of full polysomnography were conducted in the home environment.
• Twenty-six young, healthy, and carefully screened subjects participated in the study.
• Repeated measures ANOVA was employed to analyze sleep data across the four nights.

Main Results:

• While sleep duration in non-rapid eye movement (NREM) sleep did not differ between the first two nights, significant changes in spectral power were observed.
• The adaptation process for REM sleep extended up to the fourth night of recording.
• Similar adaptation dynamics were noted in NREM and REM sleep homeostasis, mirroring findings from sleep deprivation studies.

Conclusions:

• The habituation to polysomnography is a more extended process than commonly assumed, particularly for REM sleep.
• The findings suggest that the mechanisms underlying the FNE may be similar to those involved in sleep homeostasis.
• The prolonged adaptation period for REM sleep has significant implications for interpreting sleep data in psychiatric research.