Periodic limb movement disorder (PLMD) is a condition characterized by twitching, flexing, and jerking movements of the legs and arms during sleep. It’s sometimes referred to as periodic leg movement during sleep (PLMS). The movements typically occur every 20 to 40 seconds and may last for minutes or hours throughout the night. People with PLMD don’t know their limbs are moving. They’re unable to control or stop the movements. They often wake up still tired and irritable.
Researchers don’t know the exact cause of this disorder. Some researchers think it may be related to low iron levels or a problem with the nerves in the limbs caused by another condition such as diabetes. While many people with PLMD also have other sleep or movement disorders, such as restless leg syndrome (RLS), PLMD is considered a separate condition.
Although the exact cause of PLMD isn’t currently known, many researchers believe that PLMD originates in the central nervous system, but no official link has been made. The following are all thought to contribute or influence PLMD but aren’t necessarily considered a cause:
- caffeine intake
- medications like antidepressants, antinausea drugs, lithium, and anticonvulsants
- other sleep disorders such as narcolepsy or RLS
- neurodevelopmental disorders like attention deficit hyperactivity disorder and William’s syndrome
- spinal cord injury
- iron deficiency anemia
- metabolic disorders including diabetes and kidney disease
PLMD is more common among older adults. According to the Sleep Health Foundation, it affects only about 2 percent of people less than 30 years of age, but it may affect up to 40 percent of people age 65 years and older. PLMD affects men and women equally.
PLMD movements typically occur every 20 to 40 seconds in batches of 30 minutes or more during the night. They are more common in the legs but may occur in the arms as well. The limb movements typically occur during non-rapid eye movement (non-REM) sleep.
The most common symptoms of PLMD include the following:
- repetitive leg movements in one or both legs and sometimes in the arms; the movements may involve flexing of the big toe, upward bending of the knee or ankle, or twitching of the hip
- restless, unrefreshing sleep
- multiple awakenings at night
- daytime sleepiness and drowsiness
- irritability, behavior problems, and decline in performance at school or work due to lack of quality sleep
People with PLMD may also have symptoms of RLS. This may include burning or tingling sensations in the legs when they lie down. Not everyone with PLMD has RLS, but according to the American Sleep Association, about 80 percent of people with RLS also have PLMD.
Often people first become aware that they may have PLMD when their partner complains of being kicked at night, or they may find that their blankets are all over the place in the morning.
PLMD is diagnosed with a polysomnography test, also called a sleep study. This study is done overnight in a laboratory while you sleep. A polysomnogram records:
- brain waves
- heart rate
- oxygen levels in your blood
- eye movements
- other nerve and muscle functions during sleep
It’s usually done at a sleep disorders unit in a hospital or at a designated sleep center. A sleep technologist will place sensors on your scalp, temples, chest, and legs using medical glue or tape. The sensors are then connected to a computer with long wires and measurements are taken all through the night while you’re asleep.
Your doctor may also take a complete medical history and physical exam to look for other underlying issues that may be disrupting your sleep. Urine and blood samples are often taken to look for signs of iron deficiency anemia and any metabolic disorders. Low iron and metabolic disorders such as diabetes have been linked to PLMD.
Treatment for PLMD will depend on the results of the sleep study and other diagnostic tests as well as the severity of your disorder. It may also depend on whether or not you’re also diagnosed with another sleep disorder, such as RLS.
Avoiding Caffeine and Reducing Stress
You might not need treatment at all if your PLMD is moderate and does not disturb you or your partner too much. In this case, cutting down on caffeine, alcohol, and smoking can help. Caffeine isn’t just found in coffee, but also in sodas, teas, chocolates, energy drinks, and some medications, such as Excedrin.
Yoga, meditation, and other relaxation exercises may also help reduce symptoms. Massages or a hot bath prior to sleep may also help tame symptoms at night.
Treating the Underlying Condition
If you’re diagnosed with iron deficiency or another medical condition, treatment is aimed at the underlying condition. Your doctor may want to monitor your iron levels over time and may prescribe an iron supplement or recommend a diet high in iron-rich foods.
For severe cases of PLMD, medications that regulate muscle movements may be prescribed as a last resort. These may include:
- dopamine agonists, which are commonly prescribed to control tremors in people with Parkinson’s disease
- benzodiazepines such as clonazepam
- anticonvulsants such as gabapentin
Fortunately, PLMD is not a life-threatening condition. However, a good night’s sleep is important to everyone. If you suffer from PLMD or are having trouble sleeping at night, your doctor can refer you to a sleep specialist for help.