The evoked heart rate response to periodic leg movements of sleep.

STUDY OBJECTIVES: Periodic leg movements of sleep are currently subdivided based upon whether or not they are associated with EEG arousal. "Autonomic" arousals, characterized by elevations in heart rate and blood pressure without AASM-defined EEG changes, have been associated with daytime somnolence in experimental protocols. In this study, we will describe the heart rate response to periodic leg movements of sleep, both with and without associated arousals.

DESIGN: Heart rate was averaged for each of the ten cardiac cycles before, and after, the onset of individual periodic leg movements occurring in non-REM sleep for eight patients with Periodic Limb Movement Disorder (PLMD). Records were blindly scored (without EKG data) to determine if AASM-defined EEG arousals occurred within two seconds of leg movement onset. Leg movements during wakefulness were performed by four non-patient controls as a control condition.

SETTING: Sleep Disorders Center

INTERVENTIONS: None

MEASUREMENTS AND RESULTS: A significant rise in heart rate was observed following the onset of individual leg movements of sleep (N = 796), which was also significantly larger than that seen after waking leg movements (N = 275). Although heart rate elevation was 10%-40% higher when leg movements were associated with AASM-defined arousal, these differences did not reach statistical significance.

CONCLUSIONS: Periodic leg movements of sleep are associated with cardiac acceleration, even in the absence of AASM-defined arousal. It appears premature to conclude that periodic leg movements of sleep not associated with visible EEG arousal are clinically insignificant.