Coffee may prevent you falling asleep, but a new study has found then even when you do sleep caffeine can play havoc with your brain.
Researchers from the Université de Montréal, in Canada, have shown for the first time that caffeine increased the complexity of brain signals during sleep, with the impact greater in younger adults.
Professor Karim Jerbi said the study shone new light on how caffeine could modify sleep and influence the brain’s recovery, both physical and cognitive, overnight.
Professor Jerbi said they found caffeine enhanced the brain’s “criticality” during sleep.
“Criticality describes a state of the brain that is balanced between order and chaos,” he said.
“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.”
Fellow researcher Julie Carrier said caffeine stimulated the brain and pushed it into a state of criticality, where it is more awake, alert and reactive.
“While this is useful during the day for concentration, this state could interfere with rest at night. The brain would neither relax nor recover properly,” Professor Carrier said.
She said the study also showed that the effects of caffeine on brain dynamics were significantly more pronounced in young adults between ages 20 and 27 compared to middle-aged participants aged 41 to 58, especially during REM sleep, the phase associated with dreaming.
“Young adults showed a greater response to caffeine, likely due to a higher density of adenosine receptors in their brains.”
Professor Carrier said adenosine was a molecule that gradually accumulated in the brain throughout the day, causing a feeling of fatigue.
“Adenosine receptors naturally decrease with age, reducing caffeine’s ability to block them and improve brain complexity, which may partly explain the reduced effect of caffeine observed in middle-aged participants,” she said.
Read the full study: Caffeine induces age-dependent increases in brain complexity and criticality during sleep.
