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It’s common knowledge that coffee impacts sleep, but exactly how?
Researchers at the University of Montreal in Canada investigated how caffeine affects the brain during sleep, discovering that it impairs essential brain functions crucial for restorative sleep.
For the study, published in the journal Nature Communications Biology, 40 volunteers spent two nights in a sleep lab. On the first night, they received 200 mg of caffeine, and on the second, a placebo. Researchers monitored their sleep using electroencephalography (EEG) to record electrical activity in the brain.
Ingesting caffeine before sleep pushed the subjects’ brains into a state of “criticality.” Co-author Karim Jerbi described criticality in a press release as “a state of the brain that is balanced between order and chaos.” Criticality enables the brain to function at an optimal level, but it can also interfere with rest and recovery.
This should all make sense to anyone who has consumed too much coffee and then been kept up all night with a racing mind. Interestingly, for those of us who have grown more susceptible to the effects of caffeine as we age, the impact on the brain was actually more pronounced in younger subjects.
The researchers attributed the increased impact to a higher density of adenosine receptors in the younger subjects. Adenosine is a molecule that accumulates in our brains during the day, contributing to fatigue. Caffeine works by blocking adenosine receptors, thereby making us feel alert.
“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,” said co-author Julie Carrier.
