Coffee is enjoyed worldwide as a reliable morning pick-me-up and throughout the day. Yet many enthusiasts avoid it past a certain hour, fearing caffeine will sabotage their sleep.
Globally, an average of 255 kg of coffee is consumed every second. In France, a 2018 IFOP survey found 83% of people drink coffee, with 62% at breakfast. On average, French adults consume 482 cups per year. This popular beverage contains caffeine, a psychostimulant that sustains energy all day. Still, many stop after 4 p.m., believing late consumption hinders sleep.
A March 13, 2021, Metro UK article featured Verena Senn, a German neuroscientist and sleep specialist at Emma – The Sleep Company. She explains that caffeine's wakefulness mechanism doesn't necessarily impair sleep. Avoiding coffee after 4 p.m. for better rest is largely a popular belief.
As Verena Senn notes, daily activities increase adenosine production, a compound that quiets brain areas promoting alertness while activating sleep-promoting ones. Caffeine mildly blocks this, countering fatigue and boosting vigilance.
Thus, coffee may delay sleep onset, shorten total sleep time, or reduce quality. However, effects vary by individual. Not everyone responds the same.
Some can sip coffee at 11 p.m. without issue, while others must limit it to mornings. Timing matters, but quantity is crucial too—downing the equivalent of a full coffee pot daily far exceeds the risk of one or two cups.
