Ethnic difference in periodic limb movements in children.

Background: Epidemiological studies have suggested that ethnicity is a risk factor for sleep-disordered breathing (SDB) and that African-American children are three times more likely than Caucasian children to have SDB. Ethnic differences in sleep architecture and other routinely assessed sleep parameters have not been critically assessed, thus the aim of this study was to compare sleep characteristics in African-American and Caucasian children.
Methods: A total of 41,363 sleep questionnaires were mailed to parents of children aged 5-7 years in Jefferson County, KY. Parents of snoring and non-snoring children were invited to have their child undergo overnight polysomnography.
Results: Complete questionnaires were returned by 9872 families (23% response rate). Of these, 689 agreed to undergo polysomnography, and 542 complete polysomnograms were obtained (5.7% of questionnaire respondents). There were 391 Caucasian and 151 African-American children with a mean age of 6.7+/-0.5 years who underwent overnight polysomnographic evaluation. No differences between groups were observed for sleep latency, total sleep time, sleep efficiency, or rapid eye movement (REM) latency. African-American children had slightly increased stage 3 sleep (6.0+/-2.8% vs. 5.4+/-2.8%; p=0.01), although the total proportion of slow wave sleep was similar. Higher respiratory arousal index (3.6+/-6.5/h vs. 1.4+/-2.7/h; p<0.001) and total arousal index (11.5+/-5.2/h vs. 9.8+/-4.8/h; p<0.001) emerged in African-American children, who were more likely to have mild SDB (AHI>1:34% in African-American vs. 24% in Caucasian; p=0.017) and SDB (AHI>5: 22.5% vs. 7%; p<0.001). However, Caucasian children were more likely to have periodic leg movements during sleep (PLMS; 16.5% vs. 7% in AA; p=0.004). The odds ratio for a Caucasian child to have PLMS was 2.6 (95% confidence interval (CI) 1.3-5.3; p=0.006). Furthermore, in the absence of SDB, the odds ratio for a Caucasian child to have PLMS was 9.5 (95% CI: 2.2-39.9; p=0.002).
Conclusions: African-American and Caucasian children have similar sleep architecture. African-American children are more likely to display respiratory disturbances during sleep, while PLMS are significantly more prevalent among Caucasian children.