Periodic limb movement disorder (PLMD) is a sleep disorder involving repetitive, uncontrolled leg movements that disrupt a person’s sleep, causing them to feel tired during the day. In most cases, a person with PLMD doesn’t know that these movements happen while they sleep.
People of any age can have PLMD, but it’s believed to be a very uncommon condition. Usually, leg movements during sleep are triggered by another disorder, but, when limb movements during sleep appear to be the only cause of a person’s symptoms, they are considered to have PLMD.
What Are the Symptoms of Periodic Limb Movement Disorder?
People with periodic limb movement disorder repeatedly kick or twitch their legs while asleep. These are known as periodic limb movements of sleep, which is sometimes abbreviated PLMS.
These movements can involve the entire leg or may be a more subtle flexing of the ankle or toes. Some people experience twitches in the arms, but the legs are most commonly affected. Each movement lasts for just a couple of seconds but may keep occurring every 20 to 40 seconds.
Often the sleeper doesn’t even notice that the movements are happening. They may only find out about their moving at night when a bed partner tells them about being kicked or woken up.
Having periodic limb movements doesn’t necessarily mean that a person has PLMD. In addition to recurring limb movement, people with PLMD also have symptoms tied to disruption of their sleep, such as:
- Daytime sleepiness
- Feeling unrefreshed after waking up
- Difficulty falling asleep or staying asleep
- Feeling physically or mentally unwell
Children with PLMD also often have other sleep problems like sleepwalking, nightmares, and night terrors.
Many of the symptoms of PLMD, including the limb movements themselves, are common in other disorders like restless legs syndrome, narcolepsy, and sleep apnea. A person can only be diagnosed with PLMD if the limb movements during sleep are the only known cause of their daytime symptoms.
How Is Periodic Limb Movement Disorder Different From Restless Leg Syndrome?
PLMD is a similar but distinct disorder from restless legs syndrome (RLS). People with RLS experience an uncomfortable urge to move their legs while awake and while falling asleep. By contrast, those with PLMD only experience limb movements while asleep, and they don’t report sensations in their legs during waking hours.
While the conditions are different, people with RLS often have leg movements during sleep. However, in these cases, the limb movements are considered to be a symptom of RLS rather than PLMD.
What Are Causes of Periodic Limb Movement Disorder?
Researchers aren’t sure exactly what causes periodic limb movement disorder.
Usually, even if a person experiences leg movements during sleep, other issues like sleep apnea or restless leg syndrome have a much bigger impact on their sleep. However, in the rare case of PLMD, leg movements are the direct cause of sleep problems, and no other sleep disorder plays a role.
The reason for the leg movements themselves is still being studied, but they are thought to be linked to problems in the function and signaling of the nervous system. Several potential factors may play a role in the emergence of PLMD.
- Genetics: Periodic limb movements of sleep seem to run in families, particularly if there is a family history of restless legs syndrome. Researchers have found specific genes that may be linked to this sleep behavior.
- Dopamine function: People who experience limb movements in sleep often respond well to medication affecting dopamine, an important brain chemical. This suggests that problems with dopamine signaling may be a cause of the limb movements.
- Iron deficiency: Iron levels tend to be low in those who experience limb movements in sleep. Iron plays a role in how signals are sent and received in the nervous system, and iron levels can influence the function of brain chemicals like dopamine.
- Low ferritin levels: Ferritin is a protein found in cells that stores iron. Researchers have found a correlation between low ferritin levels and increased instances of periodic leg movements of sleep in older adults. A doctor can determine your ferritin levels through a blood screening panel, and develop a treatment plan to balance iron levels in the blood if needed.
- Medications: Some cases of PLMD are best explained by medication use. Medications associated with PLMD include stimulants, antidepressants, and lithium. Limb movements can also be a symptom of withdrawal from certain drugs.
PLMD has been associated with a number of other medical conditions. While it is not known if these conditions cause limb movements, people who have one or more of the following health issues may be more likely to have PLMD:
- Low iron levels
- Anemia, which is a lack of red blood cells that is frequently linked to iron deficiency
- Chronic liver or kidney disease
- Neurologic disorders, such as Parkinson’s disease
- Attention-deficit/hyperactivity disorder (ADHD)
- Spinal cord injury
In children, various conditions may be associated with PLMD, including:
- Iron deficiency
- High blood pressure
- Migraines and headaches
- Down syndrome
- Premature birth
- Sickle cell disease
- Liver transplant
Having periodic limb movements during sleep does not mean that a person has one of these underlying issues. While studies have found correlations between periodic limb movements and these health conditions, more research is necessary to understand what causes limb movements during sleep in both children and adults.
Periodic Limb Movement Disorder Diagnosis
Diagnosing periodic limb movement disorder involves several steps, including a discussion with a doctor, a sleep study, and additional tests as needed.
The doctor will ask about a person’s sleep issues and how these problems affect their daily life. If the person shares a bed with someone else, that person may be able to provide information about any observed kicking or twitching. The doctor may also ask about telltale symptoms of other conditions, like uncomfortable sensations associated with restless legs syndrome.
If a person’s symptoms could be caused by PLMD or another sleep disorder, the doctor will typically recommend a polysomnogram, or sleep study, to confirm or rule out the diagnosis.
A polysomnogram involves spending the night at a sleep lab where specialists collect precise measurements of a person’s sleep patterns and behaviors. Sensors attached to the body can detect muscle activity and limb movements throughout the night.
There are specific criteria for diagnosing PLMD based on the type of movements a person makes and how often they happen. A sleeper, bed partner, or parent can’t reliably recall the important details about limb movements that a polysomnogram reveals. A sleep study can also test for other sleep disorders associated with leg movements, like sleep apnea.
Sometimes the doctor may also have a person wear ankle movement detectors at home for several nights in case the amount of leg twitching changes from night to night. And because conditions like iron deficiency and liver and kidney failure are associated with PLMD, a doctor may also have the person take blood tests to rule out these associated diseases.
Treatment for Periodic Limb Movement Disorder
Treatment for periodic limb movement disorder often involves medication, especially for people with more severe symptoms.
Aside from medications, practicing healthy sleep habits or taking iron supplements may help treat periodic limb movement disorder. In some cases, improving sleep hygiene may be enough to resolve symptoms.
Any person with PLMD should talk with a doctor or sleep specialist who can review the different treatments that are available and their pros and cons.
Tips for Living With Periodic Limb Movement Disorder
If you or someone you know has periodic limb movement disorder, there are several strategies that may help you manage your symptoms and get a better night’s rest.
- Inform your bed partner: If you share a bed with someone, let them know that you have periodic limb movement disorder so they understand that these leg movements are out of your immediate control.
- Exercise: Exercising regularly during the day can help you sleep better at night and may help reduce symptoms of periodic limb movement disorder.
- Avoid caffeine and nicotine: These substances may make PLMD worse, so you can try cutting back on consuming them to see if symptoms improve.
- Budget time for sleep: Experts recommend that adults get at least seven hours of sleep per night, and children need even more. If you aren’t sleeping enough, this may worsen your PLMD symptoms.
- Consider your medications: Discuss the medications you are taking with your doctor since certain medications can impact PLMD.
Frequently Asked Questions About Periodic Limb Movement Disorder
Periodic limb movement disorder isn’t an immediate danger, but it may increase the risk of health problems if it is left untreated. Like other conditions that cause daytime sleepiness, PLMD may increase the risk of accidents while driving or using heavy equipment.
Some studies have found frequent periodic limb movements of sleep to be associated with a greater risk of poor health outcomes like cardiovascular disease and stroke, but more research is needed before it can be said that these problems are a danger of PLMD. A large portion of older adults experience periodic limb movements of sleep and are otherwise healthy.
While asleep, the sleeper does not have control over their leg movements, and there is no known cure for PLMD. That said, treating PLMD through medication or healthy sleep habits may reduce the frequency of limb movements.
If the limb movements are a symptom of restless legs syndrome or another sleep disorder, it’s most important to treat the underlying cause instead of the limb movements themselves.
At the same time, it should be recognized that periodic limb movements are common in healthy older adults. These movements aren’t always a sign of a medical condition that requires treatment or any effort to stop nightly leg movements.
Periodic limb movements of sleep are repetitive, automatic leg twitches that a person experiences while asleep. Periodic limb movement disorder is a specific condition in which periodic limb movements of sleep are a direct cause of poor sleep.
PLMS is a symptom while PLMD is a disorder. Every person with PLMD experiences PLMS, but not everyone who experiences PLMS has PLMD.
Hypnic jerks, also known as sleep starts, are quick, sudden limb jerks that may happen as you start to fall asleep. These movements are common, normal, and unrelated to periodic limb movements of sleep. PLMS can be distinguished from hypnic jerks because PLMS repeat periodically during the night, last for a few seconds at a time, and occur while a person is fully asleep.