Do periodic leg movements influence patients' perception of sleep quality?

Periodic leg movements in sleep (PLMS) are a common finding in various sleep disorders. Whether PLMS are an epiphenomenon or are causally related to the presence of sleep-wake disturbances is still being debated. We investigated the relationship of the occurrence of PLMS to patients' perception of sleep quality during a night of polysomnography in various sleep disorders.

The retrospective evaluation included PLMS recordings over two nights of 78 consecutive patients diagnosed with a restless legs syndrome, primary insomnia or insomnia associated with a psychiatric disorder. The subjects' perception of sleep during the polysomnography night was assessed by the subscale 'sleep quality' of the validated self-rating sleep questionnaire SFA (SFA-SQ).

SFA-SQ scores correlated with the PLMS index (number of PLMS per hour of sleep) only in patients with restless legs syndrome during the first of the two nights investigated (r=-0.464, P<0.01). PLMS appear to have a low impact on the subjects' perception of sleep quality. The correlation of subjective sleep quality to PLMS index in the first of the two investigated nights in RLS patients may reflect an adaptation effect.

The results of our study favor the hypothesis that PLMS most likely are not the primary cause of sleep disturbances in these patient groups.