Your brain may be paying the price for that late cup of coffee

For millions of people around the world, coffee is more than a beverage. It is a daily ritual, a source of comfort, and often the fuel that keeps them productive through demanding workdays.

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Whether it is a steaming cup first thing in the morning or a much-needed pick-me-up during a sluggish afternoon, caffeine has become deeply embedded in modern life.

Yet one question continues to divide coffee drinkers and sleep experts alike: how late in the day is too late to drink coffee?

For years, conventional wisdom has suggested that caffeine should be avoided after noon or, at the latest, by mid-afternoon. The concern has always been straightforward. Because caffeine is a stimulant, consuming it late in the day may make it harder to fall asleep at night.

However, emerging scientific evidence suggests that this may not be the most important question. Researchers are increasingly focusing on a more subtle issue. Even if caffeine does not stop a person from falling asleep, what effect does it have on the quality of that sleep?

Recent findings indicate that the answer may be more significant than many coffee lovers realise.

Traditionally, discussions about caffeine and sleep have centred on obvious signs of sleep disruption. These include taking longer to fall asleep, waking up frequently during the night, or sleeping fewer hours overall.

Scientists from Wroclaw Medical University in Poland argue that such measures tell only part of the story.

According to their research, caffeine's impact often extends beyond whether a person can fall asleep. Instead, it may alter what happens inside the brain during sleep, reducing the depth and restorative quality of nighttime rest.

This means that a person may spend a full eight hours in bed and still wake up less refreshed than expected.

The researchers suggest that the real issue is not simply sleep quantity but sleep quality. In other words, how effectively does the brain recover and regenerate during the night?

To understand caffeine's effects, scientists have increasingly turned to electroencephalography, commonly known as EEG.