Periodic Limb Movements in Sleep: Polysomnographic and Actigraphic Methods for Their Detection

Overview

Background.
The aim of our study was to compare the results obtained by simultaneous polysomnographic and actigraphic recording and thus to estimate the specificity and sensitivity of actigraphic evaluation of periodic leg movements in sleep (PLMS). As a standard method, PLMS are detected by means of polysomnography, including superficial EMG of anterior tibial muscles. Since 1995, there have been efforts to detect PLMS by means of actigraphy, which is more convenient for both patient and investigator. 

Methods and Results.
Recordings were done during 44 nights in 42 patients (10 women, mean age 49.2, SD 13.1 years) in our sleep laboratory. The same criteria for periodic leg movements and the cut-off periodic leg movements index (PLMI>5) were used in both methods. For the actigraphic way of PLMS detection, we found a specificity of 90 %, sensitivity 60 %, positive predictive value 88.2 %, negative predictive value 64.3 % and total diagnostic accuracy of 73.3 %. A close correlation (Spearman’s coefficient rho>0.64, p<0.0001) between PLMI resulting from either method of recording was observed, though the PLMI actigraph proved to be significantly lower (Sign test – p<0.01). 

Conclusions.
Our study has proven good specificity a negative predictive value of the actigraphic recording. To improve its sensitivity, we suggest to reduce the threshold of significant presence PLMS, as expressed by PLMI, from 5 to 3. Actigraphy seems to be a suitable method from PLMS screening in the general population for both clinical and research purposes. 

Key words:
periodic limb movements, actigraphy, polysomnography.