Periodic Limb Movement

Periodic Limb Movement Disorder (PLMD) was originally called nocturnal myoclonus by Symonds (1953). People with PLMD usually complain of difficulty falling asleep, staying asleep or excessive daytime sleepiness. They may also feel their sleep is not refreshing, have hot or cold feet, or hair wearing off their legs. The bed partners often report being kicked, fighting for bed covers, or being awakened by the movements.

PLMD should not be confounded with PLMS. PLMS is:

• a polygraphic measure obtained with anterior tibialis EMG monitoring;
• characterized by repetitive muscle contraction lasting usually between 0.5 and 5 seconds separated by an interval of 20 to 40 seconds.

The number of contractions per hour of sleep is called the PLMS index. It is considered to be abnormal when the PLMS index is greater than 5 movements per hour of sleep.

PLMD is a sleep disorder diagnosis that is given when no cause other than PLMS can be identified for insomnia or hypersomnia. However, the diagnosis of PLMD remains highly controversial. Several clinical studies failed to report significant differences on PLMS index between insomniacs, hypersomniacs and normal subjects. For example:

• Youngstedt et al (1998) studied 22 elderly subjects with complaints of poor sleep or depression. They found a high level of PLMS (median 25.8 events per hour; 86% of subjects > 5) but there was no association with sleep disturbance measures.
• Similarly, Montplaisir et al. (2000), comparing 20 insomniacs, 20 hypersomniacs and 20 normal controls did not find significant differences between these three groups on the PLMS index.

Finally, prior to our study, the prevalence for PLMD was unknown in the general population.

RESEARCH

Cross-sectional studies were performed in the United Kingdom, Germany, Italy, Portugal and Spain. Overall, 18,980 subjects aged 15 to 100 years old representative of the general population of these five European countries underwent telephone interviews with the Sleep-EVAL system. A section of the questionnaire assessed leg symptoms during sleep. The diagnosis of PLMD was based on the minimal criteria provided by the International Classification of Sleep Disorders.

RESULTS

The prevalence of PLMD is 3.9%. PLMD was higher in women than in men. In multivariate models, ***WORD MISSING HERE**** were significantly associated:

• being a woman,
• the presence of musculo-skeletal disease,
• heart disease,
• obstructive sleep apnea syndrome,
• cataplexy,
• doing physical activities close to bedtime and the presence of a mental disorder.
• being a shift or night worker,
• snoring,
• daily coffee intake,
• use of hypnotics and stress.

PLMD is prevalent in the general population. This condition is associated with several physical and mental disorders and may negatively impact sleep.

REFERENCE