Ask Dr Sleep: June 2009

About Micro-sleep

Q. Dear Dr. Sleep,

From your Sleep and Health periodical I found you – Dr. Sleep. It is very interesting to read your answers in response to readers’ questions and inquiries. Very helpful.

Now, Dr. Sleep, "micro sleep" was touched on in your past issues and I was wondering if you can talk more about it. If not, could you please talk about micro sleep in one of your future issues?

Here I have a personal experience I’d like to share with you. I remember one August day in 2001, it was an afternoon, I was driving on a highway. I was quite fatigued and my eyelids were getting heavier. I was struggling to keep my eyes open and my mind awake. Then my car came to a stop before a traffic light off the highway. My eyelids were getting even heavier. The traffic light spot was not far from my home, only a few minutes drive, so I didn’t get ready to pull over. The traffic light turned green and I turned left to my home. Then instantly, I fell into micro sleep.  I didn’t realize that all. It lasted only a few seconds. When I opened my eyes, I found my car had already drifted across the middle yellow line to the opposite traffic lane! Luckily there was no vehicle there otherwise the consequence was unthinkable! I didn’t know that it was micro sleep until last year I watched a TV program about sleep.

Dr. Sleep, could you give us readers your professional knowledge and advice this topic? Many people die of micro sleep each year. Those victims leave the world without the knowledge about it. I often think if more people’s lives, even one life, can be saved then all the time and efforts we contribute will be worthwhile.

Thank you for your attention.
Steve C. California

  1. Dear Steve,

You have touched a very important topic. Several thousands of drivers were injured falling into micro-sleep while driving and a countless number of drivers are falling asleep at stoplights nearly escaping car accidents. Several transportation accidents due to micro-sleep were described in literature, including train accidents and even the Challenger space tragedy is believed to be secondary to fatigue.

Micro-sleep means falling asleep for a few seconds in the middle of activity. The person continues the activity while sleeping – biking, driving cooking etc. Naturally, coordination is deviated and reactions to the outside environment are almost absent.

There are two types of “micro” sleep:

1) When the person’s mind is shifting into internal world, all sensors are blocking outside stimuli. The person is actually seeing a brief dream (so called REM intrusions); or is actually falling in deep-stage 2 NREM.

2) The person is going into stage one of NREM. This stage is very tricky. When we are tired, fatigued, sleepy, we feel it and could rationally make a decision to pull over. During Stage 1 NREM we do not feel that we are in sleep. We experience illusions that superimpose on reality. For example, I see that the car in front of me is moving into the wrong line or swerving, but it is you who is shifting to the wrong line and swerving. In this stage we miss our exit or find ourselves in an unfamiliar place.

The way to handle micro-sleep is to be sure to have a good restful sleep and learn about yourself to increase awareness of possible micro-sleeps.

Be Careful and drive alert.

Dr Sleep