Ten thousand meters up, over the Pacific. NASA researchers measured what actually happens when long-haul pilots are allowed to nap during cruise. As settings for a study of napping go, none could be more serious. The results survive as numbers. And the numbers are on the side of those of us nodding off at the office in mid-afternoon.
An average 25.8-minute nap lifted reactions and alertness
In this study, conducted in the 1990s by Mark Rosekind and colleagues at NASA Ames Research Center, flight crews on Pacific routes were split into two groups, one of which was given a 40-minute rest opportunity during cruise. Here is the interesting part: the crews who were given the opportunity actually slept in 93% of those opportunities. It is probably not that trained pilots are unusually quick to fall asleep. It means the fatigue of long-haul operations had built up in these professionals' bodies to a level where, given the chance, they were out within minutes. Crew members fell asleep in an average of 5.6 minutes and slept for an average of 25.8 minutes. The nap group, compared with the no-nap group, is reported to have shown a 34% improvement on a reaction-time task and a 54% improvement in physiological alertness measured by EEG, and the effect is reported to have persisted through the landing phase. A short sleep of around 26 minutes produces a measurable difference — this is the study that gave the phrase "power nap" its worldwide currency.
Past 30 minutes, the nap switches sides
That said, longer is not better. Wake up after slipping into deep sleep and a fog hangs over your head for a while (sleep inertia). That is why cutting the nap short is a skill. Japan's Ministry of Health, Labour and Welfare's "Sleep Guide for Health Promotion 2023" frames daytime sleepiness the same way: if you take a nap, keep it short and in the early afternoon. The rule of thumb is 30 minutes or less, and no later than 3 p.m. An evening nap eats into the night's sleep and manufactures the next day's drowsiness — a vicious circle.
A confession here: for a long time I regarded napping as slacking off. What changed my mind was learning that this was research done for pilots. NASA studied naps not to give crews a rest, but to fly planes safely. A nap, in other words, is not a break — it is closer to maintenance for the second half of the day. Rather than working through drowsiness on sheer grit, finishing the maintenance in 26 minutes makes the afternoon version of you reliably more useful.
The setup doesn't need to be elaborate. Seated in your chair, head down on the desk, or the car seat reclined a notch. Not lying flat is actually an advantage — it keeps you from sinking too deep. An eye mask, or even a towel laid over your eyes, changes how easily you drift off. And you don't have to fall fully asleep. Time spent with eyes closed and the outside feed shut off has value for the brain in itself — not judging success by whether you slept is the trick to keeping this habit going.
Tomorrow at midday, practice closing your eyes
- Between after lunch and 3 p.m., close your eyes for just 15-30 minutes. If sleep doesn't come, closed eyes are enough.
- Set the alarm first, and hold the 30-minute line. Staying seated, or slumped over the desk, makes it harder to sink too deep.
- Try a coffee right before the nap. Caffeine starts working 20-30 minutes later. A classic trick that times the kick to your wake-up.
If you find yourself living on naps at the cost of your nighttime sleep, that is not a napping problem. As we wrote in the snoring survey piece, the thing to question is the nighttime side.
