According to the American Academy of Sleep Medicine, there is a wide range of potential causes, including anxiety, stimulants like caffeine and nicotine, stress, and strenuous activities in the evening. It also may be facilitated by fatigue or sleep deprivation. However, most<unk> s occur essentially at random in healthy people. Nevertheless, these repeated, intensifying twitches can cause anxiety in some individuals and a disruption to their sleep onset. Sometimes,<unk> s are mistaken for another form of movement during sleep. For example,<unk> s can be confused with restless leg syndrome, periodic limb movement disorder, hypnagogic foot tremor, rhythmic movement disorder, and hereditary or essential startle syndrome, including the hyperplexia syndrome. But some phenomena can help to distinguish<unk>  from these other conditions. For example, the occurrence of<unk>  arises only at sleep onset and it happens without any rhythmicity or periodicity of the movements and EMG bursts. Also, other pertinent history allows to differentiate it. This physiological phenomenon can also be mistaken for myoclonic seizure but it can also be distinguished by different criteria such as the fact that<unk>  occurs at sleep onset only or that the EEG is normal and constant. In addition, unlike seizures, there are no tongue bites, urinary incontinence and postictal confusion in<unk> . This phenomenon can therefore be distinguished from other more serious conditions. Scientists do not know exactly why this phenomenon occurs and are still trying to understand it. None of the several theories that have attempted to explain it has been fully accepted. One hypothesis posits that the<unk>  is a form of reflex, initiated in response to normal bodily events during the lead-up to the first stages of sleep, including a decrease in blood pressure and the relaxation of muscle tissue. Another theory postulates that the body mistakes the sense of relaxation that is felt when falling asleep as a sign that the body is falling. As a consequence, it causes a<unk>  to wake the sleeper up so they can catch themselves. A researcher at the University of Colorado suggested that a<unk>  could be "an archaic reflex to the brain's misinterpretation of muscle relaxation with the onset of sleep as a signal that a sleeping primate is falling out of a tree. The reflex may also have had selective value by having the sleeper readjust or review his or her sleeping position in a nest or on a branch in order to assure that a fall did not occur", but evidence is lacking. During an epilepsy and intensive care study, the lack of a preceding spike discharge measured on an epilepsy monitoring unit, along with the presence only at sleep onset, helped differentiate<unk> s from epileptic myoclonus. According to a study on sleep disturbances in the Journal of Neural Transmission, a<unk>  occurs during the non-rapid eye movement sleep cycle and is an "abrupt muscle action flexing movement, generalized or partial and asymmetric, which may cause arousal, with an illusion of falling".<unk> s are more frequent in childhood with 4 to 7 per hour in the age range from 8 to 12 years old, and they decrease toward 1 or 2 per hour by 65 to 80 years old.
Hypnic jerk
Choking
Kussmaul breathing
Nose-blowing
Glossopharyngeal breathing
Sleep-talking
Pursed-lip breathing
Proning