Why do we sometimes have involuntary jerks while sleeping?
VIKRAM KASHYAP
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Sometimes we experience involuntary jerks while sleeping. This jerk is clinically called as hypnic jerk. It is a strange falling sensation and muscle twist. Many medical experts agree that this is a natural part of the sleeping process.
According to these experts as the muscles begin to slacken and go into a restful state as sleep is entered, the brain senses these relaxation signals and misinterprets them as indication of falling. The brain then sends signals to arm and leg muscles in an attempt to regain balance.
Even though this happens to most persons the recent studies show that hypnic jerk is linked to sleep anxiety, fatigue and discomfort.
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People who are having trouble sleeping or cannot get comfortable in bed appear to experience this more often throughout the night.
It is especially more common with people who are trying to fight falling asleep or have been deprived of sleep for more than 24 hours.
This lack of sleep from sleep anxiety or sleep deprivation confuses the muscles and the brain. The muscles continually attempt to relax and shut down for rest, while the brain remains awake creating continued ‘misinterpretations’ of falling or loss of balance.
Hypnic jerks can occur in anyone. These jerks or sleep startles normally occur at the onset of sleep, rather than at the offset. Hypnic jerks are more frequent in childhood with 4-7 per hour at the age ranging from 8 to 12 years old, and it decreases toward 1-2 per hour at 65 to 80 years old.
Various drugs and medications, notably psychoactive drugs, can create jerks when commencing sleep as the body prepares for and initiates muscle paralysis.
Opiates such as morphine, heroin and methadone have been reported to cause these jerks with regular frequency along with sudden jerking and waking during the night’s sleep. Therefore hypnic jerk, the involuntary jerks while asleep, is a kind of sleep disturbance that occurs during the non-REM sleep cycle and is an “abrupt muscle action flexing movement, which may cause arousal, with an illusion of falling.
S. PALANIAPPAN
Editor, Research Journal of Biological Sciences
J.J. College of Arts and Science
Pudukkottai, Tamil Nadu