Are periodic leg movements associated with clinical sleep disturbance?

We examined 67 patients with periodic leg movement (PLM) disorder who were seen in a university-based sleep center. The most common reasons for coming to the sleep center were insomnia, sleepiness and a request for an evaluation for possible sleep apnea. There was a significant positive correlation between PLM arousal index and age but no association with gender. Approximately one-quarter of patients were under age 30. The multiple sleep latency test (MSLT) revealed borderline normal wakefulness in the group as a whole (sleep latency of 10.2 +/- 0.9 minutes), and there was no significant correlation between the PLM arousal index and either the MSLT mean sleep latency or a measure of subjective sleepiness. Similarly, the PLM arousal index did not differentiate those who entered with chief complaints of insomnia or sleepiness. There was no significant difference in the PLM arousal index in those who reported that they did or did not awaken refreshed in the morning. In summary, in this clinical population we found no significant association between the PLM arousal index and the subjective complaint of disturbed sleep, an objective measure of daytime sleepiness or a sense of awakening refreshed in the morning. Other interesting observations included the relatively high frequency of a PLM index > 5 in patients under 30 years old and a relatively high rate of past treatment for depression.