Original ArticleThe validity of the PAM-RL device for evaluating periodic limb movements in sleep and an investigation on night-to-night variability of periodic limb movements during sleep in patients with restless legs syndrome or periodic limb movement

BackgroundThe status of night-to-night variability for periodic limb movements in sleep (PLMS) has not been clarified. With this in mind, we investigated the validity of PLMS measurement by actigraphy with the PAM-RL device in Japanese patients with suspected restless legs syndrome (RLS) or periodic limb movement disorder (PLMD) and the night-to-night variability of PLMS among the subjects.MethodsForty-one subjects (mean age, 52.1 ± 16.1 years) underwent polysomnography (PSG) and PAM-RL measurement simultaneously. Thereafter, subjects used the PAM-RL at home on four more consecutive nights.ResultsThe correlation between PLMS index on PSG (PLMSI-PSG) and PLM index on PAM-RL (PLMI-PAM) was 0.781 (P < .001). When the PLMSI cutoff value on PSG was set at 15 episodes per hour, the cutoff value for predicting this PLMSI level was 16.0 episodes per hour. When the condition was set to the level in which the mean interclass correlation coefficient reached ⩾0.9, the number of required nights for repeated measurements was 26 nights for subjects with PLMI of <15 episodes per hour and three nights for those with PLMI ⩾15 episodes per hour on PAM-RL.ConclusionsPAM-RL is thought to be valuable for assessing PLMS even in Japanese subjects. Recording of PAM-RL for three or more consecutive nights may be required to ensure the screening reliability of a patient with suspected pathologically frequent PLMS.