It has more impact on 20-somethings.
Your morning coffee might give you the boost you need to tackle the day, but new research suggests it may also be keeping your brain too stimulated at night — even while you’re asleep.
A study conducted by Canadian researchers found that caffeine can alter brain activity during sleep, particularly in young adults in their twenties. Using electroencephalography (EEG) and artificial intelligence, the research team examined how the stimulant affects the brain’s functioning during rest. The findings, published in Nature Communications Biology, revealed that caffeine increases the complexity of brain signals, especially during non-rapid eye movement (NREM) sleep — a stage important for memory and mental recovery.
The researchers explained that caffeine causes the brain to enter a state known as “criticality,” where it operates in a more alert and reactive mode. While this heightened state enhances daytime focus and decision-making, it may disrupt the brain’s ability to fully relax and repair during sleep. By increasing high-frequency brain waves typically linked to wakefulness and suppressing slower waves that support deep sleep, caffeine appears to prevent the brain from entering a truly restful state.
In the study, 40 healthy adults were given either caffeine capsules or a placebo on separate nights before bed. The stimulant had a more pronounced impact on participants aged 20 to 27, who showed greater changes in brain wave patterns. Scientists believe this is related to the number of adenosine receptors in the brain, which caffeine blocks to produce its wakefulness effect. Younger adults have more of these receptors, making them more sensitive to caffeine’s influence, while older adults experience a reduced effect due to natural receptor decline.
Given caffeine’s widespread use and its potential to alter sleep-related brain function, the researchers emphasized the need for further investigation. Understanding how caffeine affects individuals of different ages could lead to more personalized guidance on its use, particularly when it comes to maintaining healthy sleep patterns and cognitive recovery.
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