The stimulating properties of caffeine make it an unwise choice for nighttime consumption—unless you’re cramming for an exam or writing an annual report and need to stay awake. A new study from neurobiologists at the University of Montreal (Canada) has revealed how caffeine affects the brain during sleep.
Brain Stimulation Before Sleep – A Barrier to Rest
Caffeine increases the complexity of brain signals and pushes the brain into a state of criticality, the researchers noted. This means it starts processing information more effectively, particularly when it comes to learning and decision-making.
However, as the team suggested, this state interferes with restful sleep. Caffeine doesn’t just keep us alert; it actually alters brain function. Moreover, scientists found that caffeine has a more pronounced effect on young people aged 20 to 27.
This impact primarily affects slow oscillations of electrical activity known as delta, theta, and alpha waves, which are indicators of deep, restorative sleep. But caffeine weakens these waves, especially during the slow-wave sleep phase (or rapid eye movement), which the brain uses to consolidate memories and recharge cognitive abilities.
“These changes indicate that even during sleep, the brain remains in a more active but less restorative state under the influence of caffeine. The alteration in rhythmic brain activity helps explain why caffeine affects its recovery efficiency throughout the night,” said Karim Jerbi, the lead author of the study.
How Was the Study Conducted?
The team involved 40 volunteers in their research. Over two nights, they studied the participants’ brain patterns using electroencephalograms (EEG). On the first night, participants received a placebo, while on the second night, they were given a capsule containing caffeine. The capsule contained 200 milligrams of caffeine, equivalent to one or two cups of coffee.
To confirm the changes in brain activity associated with caffeine consumption, the team employed various statistical methods. The results showed a shift toward criticality and increased neuronal excitation, as reported by Science Alert.
“While this state is beneficial for concentration during the day, it hinders nighttime rest. The brain cannot relax and recover properly,” said Julie Carrier, a co-author of the study.
Why Does Caffeine’s Effect on the Brain Depend on Age?
The researchers suggested that caffeine’s impact on the brain can be explained by age-related changes.
Throughout the day, molecules of adenosine gradually accumulate in the brain, contributing to an increased sense of fatigue as bedtime approaches. Caffeine blocks the receptors that adenosine interacts with, providing a temporary energy boost. There are more adenosine receptors in younger brains, making young people more sensitive to caffeine’s effects.
“Caffeine is a psychoactive stimulant consumed daily by people of all ages in various products, such as coffee, tea, chocolate, soft drinks, energy drinks, and even pharmaceuticals,” the scientists noted in their report. Therefore, it is crucial to understand how caffeine affects the brain during sleep and how this effect varies with age. The study’s findings were published in the journal Communications Biology.