Don’t drink coffee too late—your brain won’t go to sleep

We all know coffee can make us feel suddenly awake—but what’s it doing to our brain when we’re sleeping?

A sleeping brain remains active in sleep and is less able to rest, which could affect longterm memory, if you’ve drunk coffee too close to bedtime.  The same is true for tea, chocolate and energy drinks that contain caffeine.

A research team from the University of Montreal used EEG (electroencephalography) and AI to monitor the brains of a group of 40 volunteers while they slept, and after they had drunk coffee around an hour before bed.  They were also monitored a second night when they had not had any caffeine.

Caffeine also affects a brain state known as ‘criticality’.  “Criticality describes a state of the brain that is balanced between order and chaos,” said Karim Jerbi, one of the researchers. “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.”

In a state of criticality, the brain 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.

If you’re going to have a caffeinated drink, make sure the last one is well before bedtime, and ideally in the early afternoon.

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