Drinking coffee after this time could be ruining your sleep, experts warn
That afternoon coffee could be keeping you awake at night
It feels pretty standard to wake up and turn the coffee machine on, or reach for a cup of tea straight after lunch. However, these everyday habits can have a bigger effect on your caffeine levels than you might realise, potentially making it harder to get a good night's sleep.
Recent research has found that caffeine was associated with around 45 minutes less sleep overall, with researchers looking at factors including total sleep time, how long it took participants to fall asleep, sleep efficiency and the different stages of sleep.
Perhaps most surprisingly, the researchers calculated that people should have their final coffee 8.8 hours before going to bed if they want to avoid the reduction in total sleep time seen in the analysis. So, if you're aiming to be asleep by 10pm, that would mean having your final standard coffee by around 1.12pm. For an 11pm bedtime, the cut-off would be roughly 2.12pm.
That might sound surprisingly early, particularly if an afternoon coffee is a normal part of your routine. Luke Dalton, coffee expert at UK coffee brand Contact Coffee Co, says it's a useful reminder that caffeine doesn't simply disappear because you've moved into the afternoon.
“A lot of us think of coffee in terms of morning, afternoon and evening, but caffeine doesn't work according to those neat sections of the day,” he said.
“If you're making another coffee at three or four in the afternoon, it is worth remembering that some of that caffeine can still be relevant hours later."
That said, the 8.8-hour figure shouldn't be treated as a hard rule for every coffee drinker. The study's calculation was based on a 250ml coffee containing 107mg of caffeine, but the amount you actually consume can vary considerably depending on the coffee, serving size and brewing method.
As Luke explains, “You could have a small espresso, an Americano made with multiple shots, a big mug of filter coffee or something brewed very strongly at home. They may look like similar habits on paper, but the caffeine you're consuming can be very different.
“Even the beans and the way the drink is prepared can change things, so the clock isn't the only thing worth paying attention to.”
There's some further evidence to suggest that the amount of caffeine you're drinking matters just as much as when you have it. A later trial published in the academic journal SLEEP found no significant sleep effect from a 100mg caffeine dose when taken four hours before bed in its small study. However, a much larger 400mg dose affected sleep even when consumed 12 hours beforehand.
So, rather than there being one exact time when coffee can have a negative impact on your sleep, the more useful takeaway is to consider both how much caffeine you're having and how close it is to bedtime. If you regularly have an afternoon coffee and sleep well, there's no need to panic, but if you're struggling to nod off, your later caffeine intake could be worth looking at.
