Because it happens during sleep, the person is usually unaware of the problem. In order to open the airway to breathe again, the brain needs to wake up slightly to restore muscle tone to the airway. Each time this happens, the patient’s sleep architecture becomes disrupted, which eventually leads to tiredness during daytime. This disturbance of the sleep architecture, together with the strain of sleep apnea on the heart and cardiovascular system, contributes most of the symptoms listed below.

Most people with PLMD are unaware of the movements at night, but very aware of the daytime sleepiness. Some people may also believe that they suffer from insomnia, due to their poor sleep quality or frequent awakenings, when the problem actually originates from their leg movements that disrupt their sleep.

Comprehensive polysomnography is the preferred diagnostic test for PLMD, as it incorporates electrodes that are placed directly onto the legs to monitor abnormal movements throughout the night. The effect of such leg movements on sleep quality is also measured during a polysomnogram, by correlating each leg movement with the resulting arousal response in the brain. Although PLMD and sleep apnea are unrelated disorders, they may occur simultaneously in the same person.

This excessive daytime sleepiness is sometimes difficult to distinguish from the significant tiredness that can be caused by sleep apnea or periodic limb movement disorder. The correct diagnosis, however, is very important, as the treatment is completely different for these three disorders.

Insomnia can be acute (days to weeks, usually due to some sort of stress), or chronic, lasting for more than three months and for at least three nights per week. The resulting sleep deprivation causes tiredness in daytime and may include other health consequences over time, such as irritability, depression, hypertension, diabetes, and a negative impact on concentration and memory.