Lifestyle
Caffeine, the hidden sleep thief
Caffeine has a half-life of about 5 hours. That means half of your 3 PM coffee is still in your bloodstream at 8 PM — and a quarter of it at 1 AM.
It works by blocking adenosine, the molecule that builds up through the day to make you sleepy. Caffeine doesn't remove that pressure; it masks it. When it wears off, the backlog hits.
Make it work for you
- Set a cut-off. For most people, no caffeine after 2 PM protects the night. Sensitive sleepers: stop at noon.
- Watch the hidden sources. Milk tea, soft drinks, dark chocolate, and some "energy" drinks all count.
- Delay your first cup. Coffee right on waking blunts your natural cortisol rise. Wait 60–90 minutes and it does more for less.
If you sleep badly, caffeine is the cheapest experiment you can run: move your last cup earlier for a week and watch what happens.
This article is general sleep education, not a diagnosis or personalised medical advice. If sleep problems persist or worry you, please consult a licensed physician.