Sleep Starts

Sleep starts are sudden brief contractions of the legs or arms that occur at sleep onset. They usually consist of a single asymmetric muscle contraction during a child’s transition from wakefulness to being asleep. These starts are also known as hypnic jerks. The jerks are associated with at least one of the following:

• subjective feeling of falling

• sensory flash

• a dream

The prevalence is upwards of 70%. Factors that can impact sleep starts includes:

• Nicotine

• intense evening exercise

• stress

• intake of stimulants especially excessive caffeine

They are harmless unless they cause repeated awakenings, and can rarely cause a person to develop sleep onset insomnia. It is important to distinguish sleep starts from the following conditions:

• Epileptic seizures

• Periodic limb movement

• Fragmentary myoclonus (brief jerks or twitches that occur during all sleep stages)

• Neonatal sleep myoclonus (twitching of the fingers, toes and face during infant’s sleep)