PhD Scientific Days 2025

Mental Health Sciences II.

Investigating the First Night Effect in a Healthy Population as Part of a Multiday Observational Study

Name of the presenter

Pierson-Bartel Róbert

Institute/workplace of the presenter

Institute of Behavioural Sciences

Authors

Róbert Pierson-Bartel¹

1: Institute of Behavioural Sciences

Text of the abstract

Introduction: The First Night Effect (FNE) refers to an initial deterioration in sleep quality that is commonly observed during both laboratory and home-based sleep studies. It is characterized by prolonged sleep onset latency, reduced sleep efficiency, increased nighttime awakenings, and decreased REM sleep. These changes can bias sleep measurement outcomes, making it essential to understand how quickly sleep architecture stabilizes.
Aims: This study aims to investigate the progression and resolution of the first night effect on sleep architecture over seven nights in a healthy population using home EEG monitoring.
Methods: We analyzed sleep data from 270 participants in the BSETS database, each monitored over seven consecutive nights using the Dreem 2 EEG headband. Sleep quality and architecture were assessed using linear mixed-effects (LME) modeling in MATLAB, incorporating random intercepts to account for individual differences. Night-to-night changes were evaluated through post-hoc pairwise comparisons between consecutive nights.
Results: The first night effect on sleep quality subsided by the second recorded night. Sleep efficiency increased by 1.2%, while subjective sleep quality, measured by the Groningen Sleep Quality Scale, improved by 1.6 points. However, several sleep parameters changed gradually until the fourth night. Total sleep time increased by 20 minutes per night, REM sleep duration by 8 minutes, and N2 sleep by 9 minutes. While sleep onset time did not significantly shift, wake-up time was delayed across nights.
Conclusion: The first night effect impacts sleep quality only on the initial night, with improvements in both objective and subjective measures by the second night. However, full normalization of sleep architecture, including REM and lighter sleep stages, occurs gradually and is complete by the fourth night. These findings underscore the importance of a minimum four-night adaptation period in sleep studies, particularly when investigating REM-related or psychiatric-relevant outcomes, and support more robust clinical protocol design.
Funding: Supported by the professional funding of the university research scholarship program 2024-2.1.1-EKÖP-2024-00004, financed by the Hungarian National Research, Development and Innovation Fund through the Ministry of Culture and Innovation.