Eivind Ertesvag 
A late-night cup of coffee might be more harmful than you think – especially if you fall into this specific age group.
We’ve all debated it: Can one evening cup of coffee really ruin your sleep? Now, researchers in Canada have taken a closer look – and the results are clear. One group, in particular, is most affected.
Researchers at Mila (Montreal Institute for Learning Algorithms) had 40 adults sleep two nights – one with no coffee, and one with the caffeine equivalent of 1–2 cups right before bedtime.
The result? Participants who drank coffee showed more active brainwaves during the night – and never reached deep, restorative sleep.
“Even during sleep, the brain remained in a more alert and less restful state,” explained psychology professor Karim Jerbi.
You might fall asleep – but the brain stays awake
Published in the journal Nature, the study reveals that coffee before bed not only affects how long you sleep, but also how well your brain recovers.
Caffeine suppressed slow delta waves – the kind linked to deep sleep – and boosted beta waves, typically seen when you’re awake and alert.
– “This may explain why caffeine disrupts the brain’s ability to recharge, even during sleep,” said Jerbi.
Young adults are hit the hardest
One finding stood out: young adults aged 20–27 were most affected. Their brains have more adenosine receptors – which caffeine blocks, keeping the brain artificially alert.
Older adults (41–58) were affected less.
Could impact memory and focus long-term
The study warns that regularly drinking coffee before bed could impair memory, concentration, and the brain’s ability to recover over time.
With 1 in 3 adults reportedly getting too little sleep, this study serves as a serious wake-up call. Even if you can fall asleep after coffee – your brain might not be resting at all.
So next time you’re craving an evening cup, especially if you’re under 30 – maybe skip it for the sake of your brain.
