A microsleep is a short episode of sleep that can last anywhere from 1 second to 30 seconds. They occur during times of sleepiness, generally without warning. It’s a very light sleep. Often the person having the microsleep won’t even be aware they had just nodded off.

Signs that someone is having or has had a microsleep are:

• A blank stare
• Dropping the head and jerking it back up again
• Slow frequent blinking
• A sudden jerk of the body (called a hypnic jerk)
• Not able to recall the last minute

Microsleeps can even occur when the eyes are still open.

Causes of Microsleep

Microsleep is caused by sleepiness, often combined with repetitive monotonous task such as driving or watching TV. The more sleepy you feel, the more likely you are to experience a microsleep.

When we feel sleepy, certain parts of our brain actually begin to fall asleep even while we are still awake. It’s a phenomenon known as local sleep, and it’s what causes the effects of sleep deprivation. So essentially we are still awake, but our brain is not fully functioning. Microsleep is when local sleep goes a little too far, temporarily disabling our state of awareness until the body notices what is happening and wakes us up again.

Sleep deprivation is caused by what’s called sleep debt. The longer you stay awake, the more sleep debt you acquire. The more sleep debt you have, the more sleepy you become and the easier it will be to fall asleep. Sleep debt can only be paid off with sleep. A good night’s sleep will pay off all your sleep debt, while a bad night’s sleep will only pay some of it off, bringing some sleep debt with you into the next day. A few bad nights sleep in a row will create a large accumulation of sleep debt, making you feel sleep deprived and susceptible to microsleep.

The time of the day also contributes to your feeling of alertness. The body’s circadian rhythm experiences a natural dip in alertness just before dawn and mid afternoon, increasing your chances of having a microsleep. A fifth of motorway car crashes during these times are caused by microsleep.

Dangers of Microsleep

Drowsiness is red alert!
~ Dr William Dement – Sleep research pioneer

There’s nothing wrong with briefly dropping off in front of the TV, but there can be disastrous consequences if you microsleep during a task that requires your constant attention such as when driving or operating heavy machinery

If you were traveling at 70mph and microsleep for just six seconds, you would travel nearly 200 meters whilst you were asleep. That’s more than enough distance to change lanes, cross over to the other side of the road, or pass through a red traffic light. Microsleeping when driving is surprisingly common. Multiple surveys have shown that at least 10% of people admit to having briefly fallen asleep at the wheel.

It’s not just microsleep that’s dangerous, it’s the sleep deprivation before it. Sleep deprivation affects your reactions times, judgment, and your decision making skills. It fuels recklessness, creates more stress and impatience, and worst of all, people often don’t notice their own drop in performance.

Sleep deprivation, possibly also involving microsleep, has been responsible for some of the worst well known disasters of human history, including:

• Chernobyl nuclear explosion
• Exxon Valdez oil spill
• Space shuttle Challenger explosion

A lack of sleep has also been shown to increase the likelihood of sports injuries, and has been shown to be responsible for $31 billion of workplace errors per year!

The dangers of microsleep and sleep deprivation really cannot be overstated.

Preventing Microsleep

The first step to avoiding microsleep is to become aware of how sleep deprived you are. You can use the Stanford Sleepiness Scale for a quick objective test of how sleepy you feel, or take the Epworth Sleepiness Scale to discover whether your day time sleepiness levels are considered normal or abnormal.

If you do normally feel sleep deprived during the day, instead of trying to mask the symptoms, try and find the root cause. A lack of sleep can be caused by one of the following:

• A sleep disorder – Truck drivers in particular have been shown to be at high risk from sleep apnea, and those with it have a two times higher accident rate.
• One of the causes of insomnia – Causing a build of up sleep debt which results in sleep deprivation.
• Night shifts – Combination of traveling home after a busy day and your body’s natural dip in alertness just before dawn.
• Medication – Some medication can cause drowsiness as a side effect. If you’re unsure, ask your doctor.

If you feel that you could be at risk from microsleep, try to avoid anything that requires your constant attention. If that’s not possible, take a break.

Coffee can be useful to keep you awake, although be aware that it could harm your sleep when you finally do go to bed, which could make you feel sleepy the next day. Also note that it takes around 30 minutes to feel the effects of caffeine, so ensure your break lasts for at least 30 minutes.

Taking a short nap lasting no more than twenty minutes, commonly known as a power nap, is a quick but effective way to feel more refreshed. Even a nap of just a few minutes provides surprising levels of refreshment. Just make sure you don’t nap for more than 30 minutes unless you plan on settling down for the night. Napping for over 30 minutes puts you into a deep stage of sleep which is much harder to wake up from, and you’ll probably feel even more sleepy afterwards unless you complete a full cycle of deep sleep into light sleep again, which takes around 90 minutes.

But obviously, nothing can beat a good night’s sleep when it comes to preventing microsleep.