Prevalence
RLS: 5-10% in European and North American population-based studies, lower in Asian countries. Twice as high in women than men, and increases with age.
PLMD: exact prevalence is unknown. PLMs – 7.6% of 18-65 year olds (4.5 % of total population). No sex differences.
Restless Legs Syndrome
The criteria for diagnosing RLS are based on an urge to move the legs, sometimes accompanied by an uncomfortable sensation that
(1) occurs primarily with rest/inactivity;
(2) is partially or totally relieved by movement, for as long as the movement occurs; and
(3) occurs primarily in the evening or night. Given the somewhat indescribable nature of the symptoms,
It is important to rule out other disorders, the symptoms of which may mimic those of RLS (eg, arthritis, leg cramps, and myalgias). Generally, distress, associated sleep disturbance, or impairment is required to establish the RLS diagnosis. Many individuals, when queried, will acknowledge the presence of infrequent and/or milder forms of RLS but have no associated complaint.
RLS may be precipitated or worsened by medications, particularly many antidepressants. However, when the full criteria for a movement disorder such as RLS or periodic limb movement disorder (PLMD) are met, those diagnoses, rather than movement disorder due to medication or substance, will generally be used.
Periodic Limb Movement Disorder
PLMD may accompany RLS or occur independently. This idiopathic condition is characterised by episodes of stereotypic rhythmic movement, usually of the legs, although other muscle groups (including the arms) may be involved.
PLMD may be diagnosed when the frequency of limb movement is > 15/h in adults (> 5/h in children). The periodic limb movements (PLMs) must be accompanied by sleep disturbance or other functional impairment to establish this diagnosis.
Uncertainty has existed regarding the relationship between PLMs and sleep-wake symptoms (particularly excessive sleepiness). Although PLMs are a not uncommon finding on PSG, the presence of PLMs and a sleep disturbance are not sufficient to establish this diagnosis; reasonable evidence of a cause and effect relationship between the two findings must be established.
It should also be noted that a diagnosis of PLMD should not be used in conjunction with diagnoses of RLS, narcolepsy, RBD, or untreated OSA, because the movement disturbance is a common finding in these disorders.
Citation:
International Classification of Sleep Disorders-Third Edition. Sateia, Michael J. CHEST , Volume 146 , Issue 5 , 1387 – 1394
