EEG review finds caffeine reduces deep sleep brain activity

New research reveals that caffeine consumption can significantly alter the brain's activity during sleep, reducing its restorative quality even when sleep duration appears normal. The findings, based on a review of 32 studies, suggest that caffeine reliably shifts the brain's electrical patterns toward a more wakeful state, diminishing the deep sleep essential for physical and cognitive recovery.

Scientists are increasingly using electroencephalography (EEG), a method for recording brainwave activity, to move beyond traditional sleep metrics like duration and awakenings. This technology allows researchers to assess the biological quality of sleep itself. Professor Donata Kurpas from Wroclaw Medical University, an author of the study published in the journal Nutrients, explained that EEG shows not just if a person is sleeping, but how the brain is sleeping. Quantitative EEG analysis reveals subtle changes, such as reduced slow-wave activity, which is a critical marker of sleep depth and its restorative character.

Slow waves are a key component of deep sleep, a phase responsible for bodily regeneration, energy restoration, and proper brain function. The research indicates that...