Healthcare (Commonwealth Union) – As caffeine is not limited to just coffee being present in tea, chocolate, soft drinks, and energy beverages, making it one of the most commonly consumed mind-altering substances globally, researchers of a recent study made it their focus on its impact on sleep.
In an April publication in Nature Communications Biology, researchers from the University of Montréal (UdeM) unveiled new insights into how caffeine affects sleep patterns and the brain’s ability to recover — both mentally and physically — during the night.
The study was spearheaded by Philipp Thölke, a research intern at UdeM’s Cognitive and Computational Neuroscience Laboratory (CoCo Lab), alongside lab director Karim Jerbi, a psychology professor and researcher at Mila – Quebec AI Institute.
Collaborating with sleep and aging expert Professor Julie Carrier and her team at UdeM’s Centre for Advanced Research in Sleep Medicine, the scientists employed artificial intelligence and electroencephalography (EEG) technology to explore caffeine’s impact on sleep.
For the first time, researchers demonstrated that caffeine increases the complexity of brain activity and boosts the brain’s ‘criticality’ during sleep — a state where the brain hovers between order and chaos. Interestingly, the effect was more noticeable in younger adults, noted Jerbi.
“It’s like an orchestra: too quiet and nothing happens, too chaotic and there’s cacophony. Criticality is the happy medium where brain activity is both organized and flexible. In this state, the brain functions optimally: it can process information efficiently, adapt quickly, learn and make decisions with agility.”
Carrier pointed out that caffeine activates the brain, pushing it into a state of criticality—making it more alert, awake, and responsive. While this heightened state can aid concentration during the day, it may disrupt nighttime rest, preventing the brain from fully relaxing and recovering.
Carrier’s team used an electroencephalogram to monitor the nighttime brain activity of 40 healthy persons in order to investigate the effects of coffee on the sleeping brain. On two different evenings, scientists studied the brain activity of each subject who took caffeine capsules three hours before bed and then an hour before bed, and another who took a placebo at the same times.
“We used advanced statistical analysis and artificial intelligence to identify subtle changes in neuronal activity,” added Thölke, who is the first author of the study. “The results showed that caffeine increased the complexity of brain signals, reflecting more dynamic and less predictable neuronal activity, especially during the non-rapid eye movement (NREM) phase of sleep that’s crucial for memory consolidation and cognitive recovery.”
The researchers also identified notable alterations in the brain’s electrical activity during sleep. Caffeine reduced the presence of slower brain waves, such as theta and alpha waves — typically linked to deep, restorative sleep — while increasing beta wave activity, which is more commonly observed during alertness and active thinking.
These shifts indicate that the brain stays in a more alert and less restful state even while asleep when influenced by caffeine according to Jerbi, who is also the Canada Research Chair in Computational Neuroscience and Cognitive Neuroimaging. He further indicated that this disruption in the brain’s natural rhythms may shed light on how caffeine interferes with the brain’s ability to fully recover overnight, potentially impacting memory consolidation.
The research also revealed that caffeine had a much stronger impact on brain activity in younger adults aged 20 to 27 than in middle-aged individuals between 41 and 58, particularly during REM sleep — the stage linked to dreaming.
This heightened sensitivity in younger adults is likely due to a greater concentration of adenosine receptors in their brains. Adenosine is a chemical that builds up over the course of the day, leading to feelings of tiredness.
The finding may provide valuable insights into sleep research, particularly in regards to the impact of caffeine.
