Restless Legs Syndrome and Related Disorders - Risk Factors

Risk Factors

Restless legs syndrome may affect between 2.5 - 15% of the general population. It is more common in women than in men, and its prevalence increases with age. An estimated 10 - 28% of adults older than age 65 are affected by the disorder. In about 40% of patients, RLS begins in adolescence, though it is uncommon in young children.

Family History

Up to two-thirds of people with RLS have a family history of the disorder. In such cases, it is more likely to occur before age 40. (A family history of RLS is less likely in people who develop it as older adults.) It is also more common in populations from northern and western Europe, giving added support for a genetic basis for some cases.

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Attention Deficit Activity Disorder (ADHD)

RLS and periodic limb movement disorder in children are strongly associated with inattention and hyperactivity. One study suggested that a quarter of children diagnosed with attention-deficit hyperactivity disorder (ADHD) also have RLS or 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. A 2001 study also reported an association between adult attention deficit disorder and RLS. 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 RLS, which in most cases goes away about a month after delivery. RLS in this population has been strongly associated with deficiencies in iron and with B vitamin folate (which in turn reduce iron levels).

Dialysis

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

Anxiety Disorders

Anxiety can cause restlessness and agitation at night that can cause or strongly resemble restless legs syndrome.

Other Conditions Associated with RLS

The following medical conditions are also associated with RLS, 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 simply often coexist because of other risk factors:

• Osteoarthritis. About 72% of patients with RLS also have osteoarthritis.
• Varicose veins occur in 14% of patients with RLS. Sclerotherapy treatments, in which medications are injected into affected veins, may relieve symptoms in such cases.
• Obesity
• Diabetes
• Hypertension
• Hypothyroidism
• Fibromyalgia
• Rheumatoid arthritis
• Emphysema
• Chronic alcoholism
• Sleep apnea and snoring
• Chronic headaches
• Brain or spinal injuries
• Many muscle and nerve disorders. Hereditary ataxia, a group of genetic diseases that affect the central nervous system and cause loss of motor control, is of particular interest. Some experts believe that hereditary ataxia may supply clues for genetic causes of RLS.