Risk Factors:

Restless legs syndrome (RLS) may affect 3 - 15% of the general population. It is more common in women than in men, and its frequency increases with age. The disorder affects an estimated 10 - 28% of adults older than age 65. In about 40% of patients, RLS begins in adolescence.

RLS may be more common than epilepsy and diabetes in children and teens.

Family History

As many as two-thirds of people with restless legs syndrome (RLS) have a family history of the disorder. If so, RLS is more likely to occur before they turn 40. (A family history of RLS is less likely in people who develop it as older adults.) RLS is also more common in people from northern and western Europe, giving added support for a genetic basis for some cases.

Attention Deficit Hyperactivity Disorder

Restless legs syndrome and periodic leg movement disorder in children are strongly associated with inattention and hyperactivity. Up to a quarter of children diagnosed with attention-deficit hyperactivity disorder (ADHD) may also have RLS, sleep apnea, and PLMD, and this may actually contribute to inattentiveness and hyperactivity. The disorders have much in common, including poor sleep habits, twitching, and the need to get up suddenly and walk about frequently. Some evidence suggests that the link between the diseases may be a deficiency in the brain chemical dopamine.

Pregnancy

About 20% of pregnant women report having RLS. The condition usually goes away about a month after delivery. RLS in this population has been strongly associated with deficiencies in iron and the B vitamin folate.

Dialysis

Between 20 - 62% of people undergoing dialysis report restless legs syndrome. Symptoms often disappear after a kidney transplant.

Anxiety Disorders

Anxiety can cause restlessness and agitation at night. These symptoms can cause (or strongly resemble) restless legs syndrome.

Other Conditions Associated with Restless Legs Syndrome

The following medical conditions are also associated with restless legs syndrome, although the relationships are not clear. In some cases, these conditions may contribute to RLS, or they may have a common cause. In some cases, they may coexist due to other risk factors:

• Osteoarthritis (degenerative joint disease). About 72% of patients with RLS also have osteoarthritis, a common type of arthritis affecting mostly older adults.
• Varicose veins. Varicose veins occur in 14% of patients with RLS. Sclerotherapy treatments, in which doctors inject medications into affected veins, may relieve symptoms in such cases.
• Obesity
• Diabetes -- people with type 2 diabetes may have higher rates of secondary RLS. Nerve pain (neuropathy) related to their diabetes cannot fully explain this increased rate in RLS.
• Hypertension
• Hypothyroidism (a condition in which the thyroid gland does not make enough hormones)
• Fibromyalgia (chronic pain of unknown cause)
• Rheumatoid arthritis
• Emphysema (a lung disease usually caused by smoking)
• Chronic alcoholism
• Sleep apnea (pauses in breathing during sleep) and snoring
• Chronic headaches
• Brain or spinal injuries
• Many muscle and nerve disorders; hereditary ataxia, a group of genetic diseases that affects the central nervous system and causes loss of motor control, is of particular interest. Researchers believe that hereditary ataxia may supply clues to the genetic causes of RLS.

Osteoarthritis is a chronic disease of the joint cartilage and bone, often thought to result from "wear and tear" on a joint, although there are other causes such as congenital defects, trauma, and metabolic disorders. Joints appear larger, are stiff and painful, and usually feel worse the more they are used throughout the day.

Environmental and Dietary Factors

Several environmental and dietary factors can worsen or provoke restless legs syndrome:

• Iron deficiencies. People who are deficient in iron are at risk for restless legs syndrome, even if they do not have anemia
• Folic acid or magnesium deficiencies
• Smoking
• Alcohol abuse
• Caffeine (coffee drinking is specifically associated with PLMD)
• Stress
• Fatigue
• Prolonged exposure to cold

Medications

Drugs that worsen or provoke RLS include:

• Antidepressants
• Antipsychotic drugs
• Anti-nausea drugs
• Calcium channel blockers
• Metoclopramide
• Antihistamines
• Oral decongestants
• Diuretics
• Asthma drugs
• Spinal anesthesia (anesthesia-induced restless legs syndrome typically disappears on its own within several months)

Risk Factors for Periodic Limb Movement Disorder

About 6% of the general population has periodic limb movement disorder (PLMD). Among the elderly, the prevalence increases to 25 - 58%. Studies suggest that PLMD may be especially common in elderly women. As with RLS, numerous conditions are associated with PLMD. They include sleep apnea, spinal cord injuries, stroke, narcolepsy, and diseases that destroy nerves or the brain over time. Certain medications, including some antidepressants and anti-seizure medications, may also contribute to PLMD.