A new study has revealed that the effects of drinking coffee in the evening do not always manifest as a reduction in the number of sleep hours or even difficulty falling asleep; rather, they are mostly related to sleep quality and nighttime rest. This topic has sparked widespread debate for years: what are the effects of evening coffee consumption on the brain, and consequently, on sleep quality? Some people fall asleep easily, while others toss and turn in bed until midnight.
اضافة اعلان
The findings of a growing body of research suggest that the question of whether coffee makes it too difficult to sleep is being oversimplified. According to the results of these studies, what is more important is what happens in the brain during sleep.
For these reasons, scientists studying the impact of caffeine on sleep have increasingly turned to electroencephalography (EEG), a practical method used to record brain activity. Thanks to this technology, it has become possible to monitor not only sleep duration or moments of waking up, but also the quality of the biological sleep process itself.
"EEG enables scientists to see how a person's brain sleeps," Professor Donata Kurpas from the Wroclaw Medical University said in a statement on Wednesday. She explained that traditional sleep assessment measures only sleep duration and its stages, whereas a quantitative EEG analysis reveals subtler changes, such as a decrease in slow-wave activity, which is an important indicator of sleep depth and its regenerative properties.
Slow waves are a key component of deep sleep—the stage responsible for bodily regeneration, restoring energy resources, and proper brain function.
The Effects of Caffeine
Research published in the journal Nutrients shows that the effects of caffeine do not always manifest solely in shortening sleep duration or causing difficulty falling asleep, but rather in the level of its quality. According to the findings, this means that the body might spend eight hours in bed, yet the brain does not fully regenerate its activity.
"The subjective feeling of good sleep does not always match what researchers observe through neurophysiological recordings," Kurpas said. "A person may fall asleep without significant difficulties, while the brain may show fewer signs of reaching the deep sleep stage."
According to the study, genetics, metabolic rate, age, stress levels, and chronic fatigue play an influential role in the significant variation among individuals regarding their response to caffeine.
This information is highly critical for people working in intellectual professions, athletes, and anyone who uses caffeine regularly to improve performance and focus.
Caffeine enhances alertness and reduces the feeling of fatigue, but experts point out that its effects can sometimes resemble gaining energy at specific times at the expense of the nighttime energy regeneration process.
"If caffeine helps a person perform their tasks during the day, while simultaneously leading to a deterioration in the quality of nighttime recovery, a vicious cycle may arise: greater fatigue, a higher need for stimulants, and lower quality sleep," Kurpas added.
For this reason, modern sleep research is increasingly shifting its focus toward how the brain functions during nighttime rest, rather than merely asking simple questions about sleep duration.
"Caffeine is neither good nor bad in itself. However, it is a stimulating substance for the body, and its effects depend on the timing of consumption, age, sleep quality, and stress levels," she concluded.
Asharq Al-Awsat
