Periodic limb movements during sleep: population prevalence, clinical correlates, and racial differences

There is growing interest in the study of periodic limb movements during sleep and their potential clinical correlates. The aim of the present analysis is to address the lack of population-based studies using polysomnographic (PSG) measures to determine the prevalence of period limb movements during sleep in specific racial groups as well as the general population.

A community-based sample of 592 participants drawn from the general population of tricounty Detroit (mean age = 41.9 +/- 12.6 years; 52.9% F; 31.5% African American). All individuals were assessed using objective and subjective measures in the sleep laboratory.

Participants were evaluated during a 24-h laboratory assessment, including a polysomnogram and multiple sleep latency test. Periodic leg movements were scored using standard criteria. Reports of sleep disturbance and daytime sleepiness were also assessed using standardized measures including the Global Sleep Assessment Questionnaire (GSAQ) and the Epworth Sleepiness Scale (ESS).

The overall prevalence of periodic limb movements during sleep (PLMSI >15) was 7.6%. African Americans had a lower prevalence of PLMSI >15 than Caucasians (4.3% vs. 9.3%; chi2= 4.5, P < 0.05). Regardless of race, symptoms of insomnia were significantly higher in individuals with PLMSI >15 than in those with PLMSI < or =15 (45% vs. 25%; chi2= 6.84, P < 0.01).

This is the first study to determine the prevalence of PLMS in a population-based sample using standardized objective criteria. A key finding of the present study is that racial differences in this PSG parameter do exist, with African Americans being less likely to have elevated PLMS.