The reason your body jolts when you are falling asleep

Ever wondered why your arms and legs twitch as you’re drifting off to sleep? Sometimes, these movements can be so intense – as though you’re falling – they cause you to jolt out of sleep. Well, you are not alone, as research suggests at least 70% of people experience this. Although there is no specific cause, some factors increase your tendency to get them.

Hypnic jerk

Hypnic jerk, also called sleep starts, are sudden, involuntary muscle contractions you may experience just as you are drifting into asleep. The jolt caused by the contractions can startle you into waking up when you’re in that state of being half awake, half asleep, according to Medical News Today.

Hypnic jerks are common, occur randomly and are not dangerous. A person experiencing them does not need to consult a doctor or seek medical treatment unless they cause distress or other symptoms, such as incontinence, injury, pain, or confusion.

Sleep starts usually affect only side of the body and may come in a single jerk, or multiple jerks in succession before your body relaxes again.

Plausible causes

Hypnic jerks have no clear causes and can occur in most people without any underlying explanation. However, Medical News Today says there are some ideas and theories about why these sleep starts occur including:

• Stimulants: Caffeine, nicotine and even alcohol can stay in the body for several hours, disrupting sleep. Having too much caffeine or nicotine, or consuming these substances too close to bedtime, may lead to hypnic jerks.
• Anxiety: Stress and anxiety keep your brain active when it is time to sleep. This makes sleeping less restful, causing the involuntary contractions of the muscles.
• Nighttime exercise: While exercising during the day can relax your muscles at night, evening workouts keep them active, resulting in hypnic jerks
• Sleep deprivation: If you have trouble sleeping or a lack of a healthy sleep routine, you may increase your risk of hypnic jerks

Sources used:

BBC Future: Why your body jerks before you fall asleep

Medical News Today: What is a hypnic jerk?