In a 56-year-old male with three weeks of sleep‑maintenance insomnia, sleep fragmentation, daytime sleepiness (Epworth Sleepiness Scale 13), who drinks two glasses of wine before bedtime and has a polysomnogram negative for sleep‑disordered breathing and periodic limb movements, which sleep stage finding is most likely to be observed during the second half of the night?

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Last updated: September 27, 2026 • View editorial policy

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Alcohol-Induced Sleep Architecture Changes: Decreased REM Sleep in the Second Half of the Night

The answer is (b) Decreased REM. This patient's nightly consumption of two glasses of wine before bedtime is causing alcohol-related sleep disruption, which characteristically suppresses REM sleep and increases sleep fragmentation during the second half of the night 1.

Clinical Reasoning

Alcohol's Biphasic Effect on Sleep Architecture

Alcohol metabolism creates a predictable biphasic pattern throughout the night:

  • First half of the night: Alcohol may facilitate sleep onset and initially increase slow-wave sleep (N3), creating the misleading impression of "better" sleep
  • Second half of the night: As alcohol is metabolized and blood levels decline, there is a rebound effect characterized by:
    • REM sleep suppression (the most characteristic finding)
    • Increased sleep fragmentation and arousals
    • Shift toward lighter sleep stages (N1 and N2)
    • Sleep maintenance difficulties

1 provides the most recent and comprehensive evidence (2026) demonstrating that alcohol consistently disrupts sleep architecture, particularly suppressing REM sleep and increasing fragmentation in the second half of the night, even when it may reduce sleep onset latency initially.

Why the Other Options Are Incorrect

Option (a) - Increased N3: This occurs in the first half of the night with alcohol, not the second half. The rebound effect during alcohol metabolism shifts sleep toward lighter stages.

Option (c) - Decreased arousals: The opposite occurs. Alcohol metabolism during the second half of the night causes increased arousals and sleep fragmentation, which explains this patient's sleep-maintenance insomnia 1.

Option (d) - Increased N1: While there is a shift toward lighter sleep stages, the most characteristic and clinically significant finding is REM suppression, making option (b) the better answer.

Clinical Context

This patient's presentation is textbook for alcohol-related sleep disruption:

  • Three-week duration (subacute, substance-related)
  • Sleep-maintenance insomnia with fragmentation
  • Daytime sleepiness (Epworth 13, indicating moderate sleepiness)
  • Regular pre-bedtime alcohol consumption (two glasses of wine, 9-10 PM)
  • Negative PSG for other causes (no sleep-disordered breathing or periodic limb movements)

Critical Pitfall to Avoid

Do not dismiss alcohol as a sleep aid simply because patients report it "helps them fall asleep." While alcohol may reduce sleep onset latency, it fundamentally disrupts sleep architecture and quality, particularly through REM suppression and second-half-of-night fragmentation 1. The guidelines emphasize that symptoms must not be better explained by substance effects 2, and this patient's insomnia is clearly substance-related.

Management Implication

This patient needs alcohol cessation counseling, not pharmacotherapy for insomnia. The insomnia is secondary to alcohol use, and treating the underlying cause (eliminating pre-bedtime alcohol) should resolve the sleep disturbance. Prescribing hypnotics while alcohol use continues would be inappropriate and potentially dangerous given the additive CNS depressant effects.

References

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