Despite being beloved by most folks with a deadline, caffeine’s effect on the brain when they are asleep is far from universal.
A new study from researchers in Montreal dives into how caffeine transforms our brains during sleep — and why younger people might feel the impact more.
Forty healthy adults, ages 20 to 58, spent two nights in a sleep lab after taking either a placebo or 200 milligrams of caffeine (roughly two cups of coffee). Their brain activity was monitored through a 20-channel electroencephalogram (EEG) system as they slept.
As it turns out, caffeine doesn’t just delay sleep — it also changes the brain’s internal rhythm once you are asleep. The brain becomes more “complex,” shifting toward a dynamic, high-efficiency mode known as a critical regime.
It’s like flipping a switch that makes the brain buzz with energy as though it’s awake, hitting it hardest during non-REM sleep.
Younger adults ages 20 to 27 were hit hardest by the shift. Researchers believe this is because they have a higher density of receptors caffeine targets. But before you pat yourself on the back for all those espresso-fueled late nights, there’s a catch.
This heightened brain state, while efficient, might interfere with the restorative tasks sleep is meant to handle, like memory consolidation and cellular repair. When comparing brain activity between those who had caffeine and those who did not, scientists noted machine learning could predict who had had caffeine and who didn’t, with up to 75% accuracy.
In short: Caffeine doesn’t just keep you awake — it keeps your sleeping brain awake, too. And for younger brains, that could come with hidden costs.
Health in a Heartbeat is a quick dose of medical wisdom from WUFT in Gainesville. To read previous episodes, click here.
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