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Why do people twitch when falling asleep?

It’s the end of a long day, and you finally get a chance to unwind. You lie down, close your eyes and get comfortable. You start to drift off when you’re abruptly brought back to consciousness with the quick jerk of a leg.

Walter James, M.D., a Piedmont sleep medicine physician, says these hypnic jerks or sleep starts are a totally normal phenomenon that is in no way harmful or an indication of underlying illness.

“Experiencing a hypnic jerk upon sleep onset can be compared to unplugging an electric appliance — sometimes you see a little spark,” says Dr. James. “In the same way, your muscles may experience an involuntary muscle spasm as your body transitions to a restful state.”

While these muscle spasms are not 100 percent understood, they are a common occurrence. As many as 70 percent of people experience this jerking sensation that happens when the body transitions from wakefulness to sleep. They usually only happen once, maybe twice, and they may last a half second or less. They can be very subtle or they can cause you to tumble out of bed. In this case, Dr. James says there is still no cause for concern.

Can sleep deprevation cause twitching when falling asleep?

“Individuals suffering from sleep deprivation may experience more frequent hypnic jerks,” says Dr. James. “The average adult gets only seven hours of sleep, when 100 years ago, the average good night sleep was eight hours long.”

He attributes this gradual downward spiral of our sleep habits in part to Thomas Edison’s invention of the light bulb. According to data from a National Institutes of Health survey:

  • Nearly 30% of adults reported an average of 6 hours of sleep per day. 

  • Only 31% of high school students reported getting at least 8 hours of sleep on an average school night.

Many individuals may be visited by nightly hypnic jerks without even knowing it, as the twitches often go unremembered, especially if they don't cause a person to wake up. However, if you are woken up by this distracting sensation, don’t hesitate to roll back over and catch some more zzz’s. There is no cause for concern. 

Having an established sleep routine — such as having a resting period prior to bed; avoiding food, smoking, and caffeine; and going to bed and waking at the same time — improves overall sleep.

For more information, visit Piedmont Sleep Services

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