If you think that an evening soda or caffeinated drink won’t affect you, it might be time to reconsider. New research suggests that caffeine can interfere with sleep in ways that go beyond simply reducing your sleep duration.
Researchers in Poland conducted a review of various studies to see how caffeine impacts the brain’s electrical activity during sleep. They discovered that even if people felt rested the next morning, caffeine could decrease the amount of time spent in deep sleep. This aligns with medical advice that recommends being cautious about caffeine consumption, particularly later in the day.
“Caffeine consistently modifies the neurophysiological structure of human sleep, leading to reduced sleep depth and diminished restorative effects,” the researchers mentioned in their paper, published in the journal Nutrients.
Caffeine and sleep
Caffeine is probably the most commonly used stimulant worldwide. Many people rely on it to shake off morning drowsiness or just to feel more alert. On the flip side, health professionals usually advise avoiding caffeine at least six hours before sleeping because of its potential to disrupt rest.
While numerous individuals report restless nights when consuming caffeine late in the day, some (like me, I guess) seem to be able to drink it anytime without noticeable issues. To better understand caffeine’s impact on sleep, the researchers analyzed earlier studies that involved individuals undergoing electroencephalography, or EEG, during sleep. EEGs are effective in tracking changes in brain activity throughout sleep and can reveal the quality of one’s rest.
They looked at 32 studies related to caffeine, some of which asked participants to describe their sleep quality from the previous night. Overall, a steady connection was found between caffeine consumption and decreased slow-wave brain activity, which is crucial during non-REM deep sleep—the most restorative phase. Caffeine was also associated with more wakefulness during sleep. These findings persisted even in individuals who managed a healthy amount of sleep (usually 7 to 9 hours) or reported feeling fine overall.
The researchers noted that subjective sleep quality “did not consistently align with objective disturbances—reflecting a broader trend observed in caffeine-sleep research, which indicates an imperfect understanding of caffeine’s effects on sleep,” they explained.
What to do about caffeine
The research indicates that not everyone experiences caffeine’s effects the same way. The negative impacts on sleep can vary based on factors like how much caffeine is consumed, the timing, and one’s existing sleep quality. This might mean that some individuals could benefit from limiting caffeine intake even outside of evening hours.
“It’s not just about whether coffee is consumed right before bed. For some people, the total caffeine intake throughout the day and how long it has to metabolize before night might matter too,” said study author Donata Kurpas from Wroclaw Medical University, in a statement from the university.
Other studies have found that the advantages of caffeine tend to outweigh its potential downsides as long as it’s consumed in moderation. Personally, having indulged in my share of late-night soda, this research certainly makes me think twice about that habit.
