"Don't drink coffee at lunch?" How does afternoon coffee affect the brain [Health Issue]

[Financial News] A study has been published stating that drinking more than two cups of coffee after noon can excessively activate the brain during nighttime sleep, ultimately hindering recovery functions.

Recently, researchers at the University of Montreal in Canada conducted an experiment on 40 healthy adults aged 20 to 58 to analyze how caffeine affects brainwave changes and sleep quality. Participants stayed at a sleep clinic for two days, consuming 200mg of caffeine (about two cups of coffee) one day and a placebo the other. The researchers measured brainwaves under both conditions to observe differences.

The study found that consuming caffeine after noon resulted in excessive brain activity during sleep, hindering recovery functions. This effect was more pronounced in younger individuals aged 20-27 compared to middle-aged groups.

Moreover, brainwaves showed the most significant differences during non-REM sleep. This sleep stage is when brain activity, heart rate, and body temperature all decrease, and muscles and tissues are repaired, and the immune system is strengthened. However, caffeine consumption made brainwaves irregular and complex, with unpredictable neuron activity. Consequently, physical and cognitive recovery through sleep was hindered.

Sleep progresses from non-REM sleep stages 1 to 3 to REM sleep, with non-REM stage 1 being a transitional phase between wakefulness and sleep.

If this stage is prolonged, even if you sleep, you may not feel rested. Non-REM stage 2 is a light sleep phase where information received during the day is organized, and you can easily wake up from external stimuli. If you frequently wake up or only experience light sleep during the initial sleep phase, fatigue may not be relieved even with sufficient sleep.

The research team explained that caffeine blocks adenosine receptors in the brain, suppressing drowsiness and inducing arousal. Lead researcher Professor Philippe Tolke pointed out, "If the brain cannot fully rest during sleep, core functions such as memory, learning ability, and emotional regulation may be affected."

Co-researcher Professor Julie Carrier warned, "The effects of caffeine gradually diminish two hours after consumption and can remain in the body for up to 12 hours, so coffee after noon can affect sleep that night." She added, "Coffee consumed in the morning can help improve concentration, but afternoon consumption can significantly reduce sleep quality." 

This study was recently published in the international journal Nature Communications Biology.


hsg@fnnews.com Seunggon Han, Reporter