People commonly shift and move around after getting into bed. For most of us, this movement slows once we find a comfortable position and fall asleep. But for millions of people diagnosed with a sleep-related movement disorder, nighttime movements increase before or during sleep.
According to the International Classification of Sleep Disorders (ICSD-3), sleep-related movement disorders are a category of sleep disorder in which repetitive movements interfere with sleep . These movements are usually simple, like a quick jerk or twitch. They differ from more complex movements seen in parasomnias, like sleepwalking and night terrors.
Abnormal movements can make it difficult to get sufficient, quality rest. They can also make sleep more challenging for anyone sharing a bed with someone coping with one of these disorders. Fragmented or interrupted sleep can lead to daytime consequences, such as fatigue and trouble concentrating at school or work. Understanding these conditions is a helpful first step to finding relief.
Restless Legs Syndrome
Restless legs syndrome (RLS) is a condition in which a person experiences strong, sometimes irresistible urges to move their limbs. Urges most often occur during the evening when a person is inactive. The strong desire to move or relieve these urges makes it difficult to fall asleep or go back to sleep after waking up during the night. Virtually all patients with RLS report disturbed sleep .
RLS affects between 7% and 10% of the population . People with RLS describe sensations that occur in the legs, arms, and even the neck as uncomfortable, irritating, or painful. This condition is sometimes associated with genetics, pregnancy, nutrient deficiencies, and medical conditions, but often the exact causes of RLS are unknown.
The symptoms of RLS are usually relieved by moving the affected limbs. Although there’s no single medication for more severe RLS, nutritional supplementation, medical treatments, and lifestyle changes are usually effective at reducing symptoms.
RLS only occurs while a person is awake or on the verge of sleep, but more than 80% of people with RLS also have a sleep-related movement disorder that happens during sleep—called periodic limb movement disorder.
Periodic Limb Movement Disorder
Periodic limb movement disorder (PLMD) involves repetitive movements of the arms, legs, or feet during sleep. A person with PLMD may twitch or kick for 5 to 90 seconds at a time, at least 15 times per hour. These movements may cause a person to wake up, so sleep disturbances are a common effect of this sleep-related movement disorder.
People diagnosed with PLMD don’t have conscious urges to move their limbs, nor do they experience discomfort, like people diagnosed with RLS do. The lack of urges to move and discomfort leave many people with PLMD unaware of their nighttime symptoms.
Studies have suggested that around 2% of children and 4% to 11% of adults are affected by PLMD , although the true prevalence is unknown since many people likely remain undiagnosed. A family history of RLS increases the risk of developing PLMD, as do certain nutrient deficiencies and several types of medications.
The treatment of PLMD is often similar to RLS treatment, although the American Academy of Sleep Medicine points out that there is currently insufficient evidence to make recommendations on medications for PLMD .
Sleep Related Bruxism
Bruxism is the medical term for jaw clenching and teeth grinding. Sleep-related bruxism is a sleep-related movement disorder in which a person clenches or grinds their teeth during sleep. The bite strength of up to 250 pounds of force used during teeth grinding can lead to tooth wear, pain in the teeth or jaw, and headaches over time.
Grinding often occurs on the edges of sleep, with around 80% of grinding episodes occurring when a person wakes during sleep. The prevalence of sleep-related bruxism appears to be highest in childhood, affecting between 6% to almost 50% of children . This condition becomes less common with age, affecting 3% to 8% of adults.
Sleep-related bruxism can be primary, meaning it isn’t caused by another illness, or secondary, meaning it’s caused by another condition. Conditions associated with sleep-related bruxism include psychoactive medications, certain recreational drugs, and several medical conditions (including REM sleep behavior disorder). Sleep-related breathing disorders are also associated with bruxism, with nighttime teeth grinding commonly occurring in people with obstructive sleep apnea.
In otherwise healthy people, sleep-related bruxism may not warrant treatment. If teeth grinding is causing tooth damage, headaches, or interfering with daytime activities, treatment may help alleviate pain, prevent tooth damage, and reduce clenching. Tips for coping with bruxism include home care, mouth exercises, massage, and others.
Sleep-Related Leg Cramps
Anyone who has experienced a muscle spasm or charley horse understands that muscle cramps can cause considerable pain. When these leg cramps affect sleep, they may be diagnosed as a sleep-related movement disorder called sleep-related leg cramps.
Sleep-related leg cramps involve sudden and involuntary muscle contractions that last from a few seconds to several minutes . These cramps can make it difficult to fall asleep or cause a person to wake up in the middle of the night.
Nocturnal cramps in the legs are common. In fact, up to 60% of adults report experiencing this painful nighttime symptom. Sleep-related leg cramps may be caused by muscle fatigue or nerve issues, underlying medical conditions, certain medications, and common daytime activities. Daytime activities that increase the risk of leg cramps include standing for long amounts of time and intense exercise.
Fortunately, sleep-related leg cramps are often relieved by stretching, massaging, or applying heat to the affected muscles. In those requiring additional relief, treatment may focus on addressing underlying medical conditions and trying potentially helpful medicines, although medications are not always effective for this condition.
Sleep-Related Rhythmic Movement Disorder
Sleep-related rhythmic movement disorder (SRMD) is a condition characterized by repetitive, rhythmic movements occurring when a person is drowsy or during sleep. These movements are most often body rocking, where a person moves their entire body, headbanging, or head rolling. People diagnosed with SRMD often hum or make sounds during these movements.
Rhythmic movements during sleep are common in infants, affecting up to 66% of babies , and isn’t always considered a disorder. A person may be diagnosed with SRMD only if their movements interfere with sleep, cause impairment in daytime activities, or lead to injury. Only 5% of children continue to have rhythmic movements during sleep at 5 years old. This condition is rarely seen in adolescents and adults.
Stimulation of the vestibular system, or inner ear, may be one reason RMD occurs in some infants and toddlers. The vestibular system affects balance. Self-stimulation of this system has been found to be calming in infants, toddlers, and children with autism or intellectual disabilities. In fact, RMD may be a calming strategy used in some children to combat insomnia.
Management of this condition is often guided by a doctor or specialist’s clinical experience and published studies of individual cases.
Other Sleep-Related Movement Disorders
Benign Sleep Myoclonus of Infancy
Benign sleep myoclonus of infancy (BSMI) is characterized by twitches or jerks that occur when an infant is drowsy or asleep, beginning anywhere from the first day of life to 3 years old . This rare movement disorder is sometimes mistaken for other conditions like epilepsy. Unlike more serious conditions, BSMI symptoms stop when an infant is woken up. Treatment for this condition is usually unnecessary as it resolves in two-thirds of affected infants by 3 months old .
Propriospinal Myoclonus at Sleep Onset
Propriospinal myoclonus at sleep onset (PSM) is a movement disorder in which a person experiences sudden jerks of the neck and abdomen when drowsy or trying to fall asleep . While the abnormal movements may cause a person to have trouble falling asleep, they resolve when a person either falls asleep or wakes up completely. PSM may be primary, and not caused by an underlying condition, or secondary, as a result of a spinal or nerve-related condition. Treatment for PSM often targets the underlying causes of this condition.
When To See a Doctor
Getting sufficient, quality sleep is important for people of all ages. Losing sleep can affect our thoughts and emotions and increases the long-term risk of mental and physical health issues. Many people with sleep-related movement disorders experience insufficient and poor quality sleep, sometimes without understanding the cause of their symptoms. For this reason, it’s important for anyone with sleep-related concerns to talk to a doctor or sleep specialist.