What is Periodic Limb Movement Disorder?

Periodic limb movement disorder (PLMD) is a condition where a person’s limbs move repetitively during sleep, which can severely disrupt the person’s sleep. It was formerly called sleep myoclonus or nocturnal myoclonus.

The limb movements normally occur during light, non-rapid eye movement (non-REM) sleep. The movements occur about every five to 90 seconds, with nightly variations in the limbs involved. The limbs affected are most commonly the lower extremities; the most common movements are a repetitive straightening of the foot or the leg at the knee. However, in some patients upper extremities are also affected.

Like other sleeping disorders, a person with PLMD is often unaware of their involuntary movements. In many cases, the condition goes unrecognized until reported by a sleep partner.

PLMD Causes and Treatments

Many people (over 30 percent of adults over 65 years old) suffer from occasional periodic limb movements during sleep, but most of the time, these periodic limb movements are caused by another condition. True PLMD (when periodic limb movements are not caused by another condition) is rare.

The causes of the condition are unknown, but it is known that PLMD is more common in patients with the following conditions:

  • narcolepsy
  • Parkinson’s disease
  • diabetes
  • spinal cord injuries
  • REM sleep behavior disorder

Some medications appear to worsen PLMD, including some antidepressants, antihistamines, and antipsychotics. Nevertheless, no one should stop taking any medication without consulting their doctor first.

PLMD is less studied than other sleep disorders, and it is unknown how prevalent it is in society. While it can happen at any age, the disorder appears to happen more in older people.

Periodic limb movement disorder can be treated with narcotics, anticonvulsant medications, benzodiazepines, and drugs used to treat Parkinson’s disease. Usually, in treating the disorder, medical professionals have patients avoid caffeine and caffeine-containing products like chocolate and caffeinated beverages.