How Coffee Influences Sleep and Brain Function

Coffee, a popular beverage enjoyed worldwide, contains caffeine, a psychoactive substance that can significantly impact sleep quality and brain activity. Recent research published in Communications Biology by scientists from the University of Montreal sheds light on how caffeine alters neural processes during sleep, affecting both physical and cognitive recovery overnight.

The study, led by Philipp Thölke and Karim Jerbi, utilized advanced electroencephalography (EEG) combined with artificial intelligence to analyze brain signals during sleep. They discovered that caffeine increases the complexity of brain activity and enhances brain 'criticality,' a balanced state between order and chaos that promotes optimal brain function. This effect was particularly more pronounced in younger adults aged 20 to 27.

Criticality refers to a state where the brain operates efficiently, capable of processing information, adapting, learning, and making decisions seamlessly. Caffeine stimulates the brain, pushing it into this critical state, which in daytime leads to alertness and concentration but may interfere with restful sleep at night, preventing proper relaxation and recovery.

The researchers compared brain activity during sleep on nights when participants consumed caffeine capsules before bedtime to nights with a placebo. They observed that caffeine increased the dynamic complexity of neuronal activity during non-REM sleep and altered rhythmic brain waves—attenuating slow oscillations like theta and alpha waves, which are associated with deep, restorative sleep, while stimulating beta waves linked to wakefulness and cognitive activity.

Importantly, the effects of caffeine were more significant in young adults due to a higher density of adenosine receptors in their brains. Adenosine, a molecule that promotes sleepiness by accumulating during wakefulness, is blocked by caffeine. As age increases, the number of these receptors decreases, reducing caffeine’s impact on brain activity, which suggests that younger individuals are more susceptible to caffeine’s stimulating effects and potential sleep disruption.

These findings highlight the importance of understanding caffeine's neural effects, especially given its widespread consumption as a fatigue remedy. Recognizing age-related differences in caffeine’s impact may help in developing personalized guidelines for caffeine intake, ensuring better sleep quality and brain health.

Source: https://medicalxpress.com/news/2025-05-coffee-affects-brain.html