What you’re describing is a condition called sleep myoclonus, a sophisticated term referring to the involuntary contraction of muscles, which is what causes your girlfriend to twitch in her sleep. Most people who have this condition don’t realize they are twitching. The movement occurs early in the sleep cycle and may be caused by stimuli such as loud sounds or the stirrings of a bed partner. It’s not clear what causes myoclonus, but for severe cases a doctor can prescribe medication.
- Some scientists say that factors such as stress, fatigue, and sleep deprevation can impact the regularity of myoclonus, but there has not been decisive research on the topic.
- One hypothesis suggests that these small movements in sleep are the part of the body’s natural transition out of the alert state, and occur as a result of misfiring nerves during that process.
- Another prevalent idea examines the topic from an evolutionary angle, suggesting that the muscle spasms originate from a prehistoric primate reflex to muscles relaxing as the body goes to sleep – the brain misconstrues the slackening of muscles as a sign that the sleeping primate is falling, and causes the muscles to respond.
While sleep myoclonus is an innocuous condition, it can be linked with other sleep disorders, such as sleep apnea and restless leg syndrome. If you notice that your partner stops breathing in their sleep, or if they wake up without feeling rested, they may have sleep apnea and should seek treatment. There are doctors who specialize in sleep disorders who can help determine a diagnosis. Neurologists often treat patients with restless leg syndrome; the patients often report the twitching you described, but also an inability to keep their legs still and a feeling of tightness.
Reference:
http://www.livestrong.com/article/136391-why-do-people-jump-while-sleeping/