The reason for the sudden body jerk during sleep

Sudden body jerks during sleep, medically referred to as "hypnic jerks" or "startle reflex," are typically normal phenomena caused by the nervous system when entering the deep sleep stage. As the body transitions from wakefulness to deep sleep, muscles undergo a relaxation process and occasionally experience sudden contractions, resulting in abrupt body movements. The causes may be multifactorial, including both physiological and pathological factors. Physiological factors such as excessive fatigue, mental stress, and poor sleep quality may lead to instability in the nervous system during sleep, thereby causing brief body jerks. Pathological factors may involve medical conditions such as hypoglycemia, calcium deficiency, restless legs syndrome, and epilepsy, which can trigger abnormal body movements during sleep. If hypnic jerks occur frequently and affect sleep quality, it is advisable to consult a doctor promptly.