https://doi.org/10.3390/nu18081220
A cup of hot coffee in the morning to dispel drowsiness and a refill in the afternoon to withstand work fatigue have become the norm in the lives of countless people.
Many people console themselves that as long as they don't drink it before bedtime, caffeine won't disturb their sleep.
But a systematic review broke this lucky streak:
Even if you drink coffee normally during the day, it will significantly compress the duration of deep sleep, and the quality of nighttime sleep will visibly decline.
This interpretation is based on the authoritative review "The Caffeine Brain Part 2: The Effect of Caffeine on Sleep Related Electroencephalography (EEG) – A Systematic and Mechanical Review".
The research team integrated multiple electroencephalogram (EEG) monitoring data to dissect the complete mechanism by which caffeine erodes high-quality sleep from the level of brainwaves, and the conclusion breaks away from the inherent cognition that "drinking coffee before bedtime only harms the body".
Many people mistakenly believe that caffeine only delays bedtime, but EEG testing provides more detailed results.
Sleep is divided into three stages: light sleep, deep slow wave sleep, and rapid eye movement sleep. Deep slow wave sleep is responsible for body repair, energy storage, and memory consolidation, and is the core of determining whether to relieve fatigue after waking up.
Experiments have shown that subjects who regularly consume caffeine during the day experience a significant decrease in the amplitude and duration of deep sleep brain waves at night. Even if the duration of falling asleep does not change, the entire night's sleep is only a "false sleep".
From a physiological perspective, caffeine competitively binds to adenosine receptors in the brain.
Adenosine is a key substance in the human body that accumulates drowsiness and triggers deep sleep. After the receptor is occupied, the brain cannot receive signals of fatigue, and even at night, the nerves remain in a mildly excited state, unable to smoothly switch to deep repair mode.
What is even more alarming is that the half-life of caffeine can reach 4-6 hours. If consumed multiple times during the day, caffeine in the body will continue to accumulate, and residual doses in the evening can still interfere with nighttime EEG activity.
Some coffee enthusiasts may have the illusion that they can still fall asleep after drinking coffee, which is essentially a passive prolongation of shallow sleep duration and a continuous lack of deep repair processes.
Long term exposure to this can lead to chain reactions such as morning fatigue, emotional distress, and decreased focus. During the day, one can only rely on more coffee to forcefully refresh themselves, falling into a vicious cycle.
You don't need to completely quit coffee, adjusting your drinking boundaries can balance your needs:
Control 1-2 cups per day, no longer consume after 3pm, and reduce high concentration caffeine drinks such as espresso and energy drinks.
Refreshing and sleeping are not opposed to each other. Finding the right rhythm is the key to retaining the comfort of coffee and maintaining a peaceful deep sleep throughout the night.
https://doi.org/10.3390/nu18081220
For more related information, you can scan the code and join the group to invite you into the academic circle
Original title: "Research finds that drinking coffee every day can greatly reduce deep sleep"