Sleep Disorders  Restless Leg Syndrome Limb movements can also negatively affect one's ability to fall asleep or stay asleep, thus making these limb movements Dyssomnias. Restless Legs Syndrome (RLS) occurs when lying down to go to sleep. It is often described as a "creepy, crawly" feeling in the legs, with an irresistible urge to move the legs. Five to fifteen percent of population will experience RLS at some point in their lives. RLS is more common in the older adult population, and may be more common in women. There appears to be a genetic predisposition for RLS. This syndrome s diagnosed based on self-report, and is treated with medication. Periodic Limb Movement Disorder (PLMD) Myoclonus is also known as Periodic Limb Movement Disorder (PLMD) or "PLM's". PLM's are limb (usually leg) jerks or movement during sleep. These movements are regular, occurring 20 to 40 seconds apart. These limb movements occur during NREM sleep, and disrupt the sleep pattern by causing arousals from sleep. PLM's may also cause insomnia and daytime sleepiness. PLM's become more common with age. It is estimated that 35% of people over 60 years have PLM's. PLM's are equally common in men and women, and often coexist with RLS. PLM's are normally diagnosed as part of a sleep study, and are treated with medication.