The aim of this study was to evaluate and statistically describe the age-related changes in leg movements (LMs) during sleep in a large group of subjects with restless legs syndrome (RLS).
One hundred eight untreated patients affected by idiopathic RLS were included in this study (mean age 52.0years, min 7.5, max 83.2years). The time structure of their polysomnographically recorded LMs was analyzed using an approach particularly appropriate for assessing their quantity, periodicity, and distribution during the night.
Periodic LMs during sleep (PLMS) increased in number gradually in the age groups. Their typical interval was approximately 24-28s before the age of 55years but at approximately 14-16s after the age of 65years. PLMS index reached a plateau at 15-25years of age and remained stable up to 65years; after this age, it showed an important increase. Periodicity index (PI) increased progressively up to the age of 35years and then remained stable up to the age of 85years. No correlation was found between PLMS index and PI. The number of PLMS per hour of sleep declined through the night in subjects aged 15-75years; after this age, PLMS tended to be equally distributed across the entire night.
The use of three main parameters derived from the analysis of leg motor activity during sleep in RLS patients (PLMS index, PI and PLMS time distribution) is capable of providing us with important information about the age-related changes of PLMS in this condition, which can be used in the evaluation of the sleep motor patterns in these subjects.