First-Night Effect in Sleep Studies

The first-night effect (FNE) describes the consistent reduction in sleep quality observed when individuals spend their initial night in a novel environment, such as a sleep laboratory or unfamiliar accommodation. Manifestations include increased wakefulness after sleep onset, lower sleep efficiency and a reduction in deep slow-wave sleep, often accompanied by regional alterations in brain activity. The FNE arises from an adaptive hypervigilance of central and autonomic systems when confronted with unfamiliar surroundings. Although it typically attenuates over subsequent nights, its magnitude is influenced by individual traits, age and clinical status. Recognising and accounting for the FNE is crucial for optimising experimental design, ensuring the validity of cross-night comparisons and refining clinical polysomnographic assessments.

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First-Night Effect in Sleep Studies publication trend

The graph below shows the total number of articles in first-night effect in sleep studies across all publications each year (not limited to Nature Index journals).

Technical terms

First-night effect: Disruption of sleep quality and architecture during an initial night in a novel environment, marked by increased arousal and fragmented sleep.

Sleep architecture: The temporal organisation of sleep stages and cycles, encompassing transitions between non-rapid eye movement and rapid eye movement sleep.

Polysomnography: A multimodal recording of physiological signals—such as brainwaves, eye movements and muscle tone—used to classify sleep stages and detect disturbances.

Electroencephalography (EEG): A technique for measuring electrical activity of the brain via scalp electrodes, enabling spectral analysis of sleep stages.

Heart rate variability (HRV): The fluctuation in time intervals between successive heartbeats, reflecting autonomic nervous system balance during sleep.

References

1. Examining First Night Effect on Sleep Parameters with hd-EEG in Healthy Individuals. Brain Sciences (2022).
2. Discrepancies in the Time Course of Sleep Stage Dynamics, Electroencephalographic Activity and Heart Rate Variability Over Sleep Cycles in the Adaptation Night in Healthy Young Adults. Frontiers in Physiology (2021).
3. The First-Night Effect on the Instability of Stage N2: Evidence from the Activity of the Central and Autonomic Nervous Systems. Brain Sciences (2023).