Caffeine’s Effects May Continue During Sleep

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Caffeinated beverages like coffee, tea, and cola may help keep you alert during the day, but they may also interfere with some aspects of healthy slumber. According to recent research by researchers at Université de Montréal, caffeine can also affect quality of sleep and brain recovery. They found that caffeine increases brain signal complexity and stimulates a state called “criticality,” where brain activity is balanced between order and chaos. While helpful for alertness during the day, this state can interfere with the brain’s ability to rest and recover during sleep.

In an experiment with 40 healthy adults, participants who consumed caffeine before bed showed more dynamic brain activity, especially during non-REM sleep — a stage important for memory and cognitive recovery. Caffeine reduced the slow brain waves linked to deep sleep and increased beta waves, which are typically seen during wakefulness.

The effects were more pronounced in adults in their twenties, likely due to their higher density of adenosine receptors, which caffeine blocks to reduce fatigue. Middle-aged participants (ages 41 to 58) were less affected.