Afternoon coffee may impair brain recovery even after eight hours of sleep
New research indicates that caffeine consumed later in the day can reduce deep sleep quality, even if total sleep time is sufficient.
Many people believe that the main downside of coffee is difficulty falling asleep. However, recent studies reveal that caffeine can affect brain restoration even when nighttime sleep duration is normal.
In a study published in the journal "Nutrients," researchers used electroencephalography (EEG) to analyze sleep quality and found that caffeine can reduce slow-wave activity – a phase crucial for energy restoration and memory consolidation.
Co-author Donata Kurpasa explains that subjective feelings of good sleep often do not match neurophysiological measurements. A person may fall asleep easily and not wake up during the night, yet their deep sleep indicators may be weaker. Over time, this can lead to accumulated fatigue, reduced concentration, and worsened overall well-being.
Experts note that individual responses to caffeine vary – influenced by genetics, age, caffeine metabolism, and stress levels. Some people can drink coffee late in the evening without noticeable effects, while for others, even an afternoon cup may affect sleep quality.
Researchers warn of a potential vicious cycle: if a person feels tired and uses coffee to improve daytime functioning while impairing nighttime recovery, fatigue may increase along with the need for stimulants. If you still feel tired after eight hours of sleep, it may be worth evaluating not just sleep duration but also the timing and amount of coffee consumption.
