Microsleep and Power Naps

The accident happened because the driver fell asleep. How can so many people fall asleep while driving, I’ve always wondered?! Turns out my question is valid, as Matthew Walker writes in his wonderful book, Why We Sleep. The number of people “falling completely asleep at the wheel” is rare. (That would require severe sleep deprivation, 24 hours or longer without sleep).

What’s far more common is something called “microsleep”:

“During a microsleep, your brain becomes completely blind to the outside world for a brief moment – and not just the visual domain, but in all channels of perception.”

It is suffered by individuals who are chronically sleep restricted (getting less than 7 hours of sleep on a regular basis). Scarily, a microsleep lasts for as little as 2 seconds. Yes, that’s right: 2 seconds. And you don’t even realize it happened most of the time… unless you have an accident.

As Walker writes, this explains why drowsy driving causes more accidents than those caused by alcohol and drugs combined. Surprised? Then check out the logic behind the fact:

“Drunk drivers are often late in braking, and late in making evasive maneuvers. But when you fall asleep, or have a microsleep, you stop reacting altogether.”

Now consider those long-haul flights, where the pilot probably wouldn’t have slept enough (or well) and is trying to land the plane. Are you worried now that you know about microsleep? In the 1980’s and 90’s, David Dinges was asked by the FAA (US aviation regulatory body) to deal with practical realities: if pilots will inevitably be in such situations, and they can get only a short nap opportunity (40 – 120 minutes), when should they take it? Close to landing time? Before take-off? Or somewhere in the middle? The counter-intuitive answer was “before take-off” (it works better if you delay the onset of sleep deprivation rather than trying to sleep a little once sleep deprivation is kicking in/has already kicked in).

So Dinges recommended making “prophylactic naps” mandatory on such flights. The FAA ok’ed the recommendation but didn’t like the name given. So Dinges suggested calling it “planned napping”. Nah, said the FAA, it sounds too “management-like”. And so the FAA coined the term “power nap”. And thus the term was born and the practice institutionalized for pilots.

A side-effect of the term “power nap” has been the wrong impression it conveys. No, a 20-minutes power nap does not enable you to sacrifice regular 8 sleep windows and still perform at your best. But try telling that to corporate executives…