Comorbidities in children with elevated periodic limb movement index during sleep

STUDY OBJECTIVES: Little is known about comorbidities in children who have elevated periodic limb movement index (PLMI) during overnight polysomnogram (PSG). The aim of this study is to identify comorbidities in children with elevated PLMI (PLMI >5) versus children with PLMI <5 presenting to a pediatric sleep center.

METHODS: This study was a retrospective review of all clinically indicated PSGs obtained consecutively from 3/2017-3/2019 at Seattle Children's Sleep Disorders Center. Data collected included: demographics, clinical presentation, medications, medical history, family history specifically for restless legs syndrome (RLS), ferritin levels, and PSG metrics. Characteristics between those with (cases) elevated PLMI (AASM criteria) and without (controls) were summarized.

RESULTS: We identified 148 subjects with elevated PLMI (67% male, mean age 7.95 years, range 1-20), yielding a PLMI > 5 prevalence of 5%. There were 188 controls included (58% male, mean age 8.0 years, range 1-19). Neither sex (Chi-square=2.8, NS) nor age (Mann-Whitney U=1339.5, NS) differed between groups. Case subjects had a higher prevalence of RLS, snoring, insomnia, mood disorders, behavioral problems, morning headaches, chronic kidney disease, epilepsy, and chronic heart disease. Similarly, the use of antidepressants, antipsychotics, anti-seizure medication, and other medications was statistically more frequent in children with elevated PLMS. The prevalence of PLMI>5 was 5% and the prevalence of periodic limb movement disorder (PLMD) was 0.3% in children referred to polysomnography. Ferritin levels did not differ.

CONCLUSION: We identified the prevalence of PLMD in a sleep medicine referred population. We have also identified comorbidities and medications associated with elevated PLMI in children.