Every day after lunch, you find yourself overcome by drowsiness and you can’t get any work done because all you want is to crawl under your desk and go to sleep. Why does this happen?
This universal phenomenon, known as the “post-lunch dip,” represents a collision of biology and economics. It is natural for human beings to want to sleep about seven hours after they have awakened. But, as the internal rhythms of the body call out for rest, the efficiency of the modern workplace demands exertion.
Do all people experience the post-lunch dip?
The effect may be natural, but “not everyone experiences it with equal intensity,” said David F. Dinges, a professor and sleep scientist at the University of Pennsylvania School of Medicine. A few people say they don’t feel the dip at all, while others—about 15-20% of the population, he estimates—are “closet nappers”. These are the ones who steal into empty rooms or their parked cars, or fall asleep at their desks because they can’t fight off the urge to close their eyes.
Often, these people are ashamed of their behaviour because it is associated with laziness, Dinges said. But by giving in to the urge, they are actually improving the quality of their work.
Can being drowsy at work affect productivity and quality?
Yes. A study of drivers found that more car accidents occur during the afternoon dip than at noon or 7pm, Dinges said. Few studies have been done on drowsiness in the workplace, but it seems likely that more errors in judgement are also occurring in offices, on factory floors and in other work environments at this time.
If possible, workers who are unable to take a nap should try to perform more mundane tasks during the dip and save projects that require the greatest accuracy, mental acuity and creativity for other times of the day, said Fred W. Turek, a biology professor and director of the Center for Sleep and Circadian Biology at Northwestern University.
Can a short nap really help?
For some people, yes, and the older you are, the less time you need for a nap to be beneficial, Dinges said. But in order to nap effectively, your head must be able to rest on something, he said, such as a desk or the back of a chair.
If you can’t take a nap, how can you ease the effect of the post-lunch dip?
Many people self-medicate their way through the dip with coffee, Turek said, which helps explain why caffeine is the most-used drug in the world. But responses to caffeine vary and, for some people, it can disrupt night sleep.
Another way to push through the dip is to exercise or simply get up and move around the room. If you need to talk to a colleague at another desk, this could be the ideal time, said William C. Orr, president of the Lynn Health Science Institute in Oklahoma City and an expert on sleep disorders. It also helps to arise at the same time every morning, Dinges said. He has found that getting up earlier than usual—even as little as a half-hour earlier—increases drowsiness in the afternoon.
Above all, it is important to get a good night’s sleep. With that rest as a backbone, Zee said, “One will naturally begin to feel more alert within a couple of hours” after the dip begins. “Your circadian alerting signal will kick in as the day goes on,” she added, “and it gets higher and higher until about an hour or so before bedtime.”