Caffeine Can Disrupt Sleep Without Keeping You Awake
Caffeine may make sleep less restorative even when people fall asleep normally and stay in bed for eight hours; EEG recordings revealed fewer of the slow brain waves associated with deep sleep. Individual sensitivity varies dramatically, meaning that for some people even caffeine consumed earlier in the day could affect nighttime recovery.
1. What the Research Says
The study relied on EEG recordings of brain activity during sleep. How strongly caffeine affects any single person cannot be derived from it.
2. How It Fits Earlier Research
Earlier studies point in the same direction: caffeine can reduce deep sleep and slow brain waves, while sensitivity varies from person to person. The new study adds that this may occur even when someone falls asleep normally and stays in bed. Coffee, caffeine, and sleep: A systematic review of epidemiological studies and randomized controlled trials. (2017) · The effect of caffeine on subsequent sleep: A systematic review and meta-analysis. (2023) · A naturalistic investigation of the effects of day-long consumption of tea, coffee and water on alertness, sle (2000)
3. Source
ScienceDaily: Coffee doesn’t have to keep you awake to disrupt your sleep (2026-09-22)
Full evidence overview: Caffeine
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