You probably know how it goes. You've just had lunch and you're back at your desk. 3pm rolls around and home time is still some way off. Then the yawns start and all you can think about is curling up under your desk for a sleep. It's a fairly normal response, and the subject of an abstract at Sleep 2008, the 22nd Annual Meeting of the Associated Professional Sleep Societies. A group of scientists from Loughborough University in the UK presented their work on daytime sleepiness, and whether the best way to combat it was to get up later in the morning, caffeine, or a 20-minute afternoon nap.

The study involved 20 healthy adult volunteers, who all averaged around 7.4 hours sleep a night. They then compared how the volunteers performed to multiple sleep latency testing—how long it took them to fall asleep for a nap at various intervals—in one of four states; their normal amount of sleep,after having an extra 90 minutes in bed in the morning, after taking 150 mg of caffeine at 2pm, or after taking a 20-minute nap at 2:30pm.

Compared to getting an average night's sleep, all three of the conditions extended the amount of time it took the subjects to fall asleep during the sleep tests, but the 20-minute afternoon nap proved the most effective at combating sleepiness later in the day; although a long lie-in in the morning and the caffeine also reduced afternoon sleepiness, they did so less effectively than the 20-minute nap.

So, there you have it. Afternoon tiredness is best combated by a quick nap. Of course, for those of us who aren't lucky enough to work at home, have a very understanding boss, or live in Spain, two cups of coffee might be a better idea...

Sleep, 2008. 31 A131, 0395.