MINNEAPOLIS – Using the adult treatment threshold for serum ferritin to guide treatment in children with restless sleep may lead to inappropriate iron supplementation.
In both adults and children, iron deficiency has been linked to the presence and severity of restless legs syndrome (RLS) and periodic limb movements of sleep (PLMS). For adults, a serum ferritin less than 50 mcg/L is the threshold commonly used to guide iron supplementation for patients with RLS or PLMS. A threshold of 40-50 mcg/L also has been used in pediatric studies.
For children, however, a far lower level of 20 mcg/L appears more appropriate, Alyson Connor reported at the annual meeting of the Associated Professional Sleep Societies.
"Our findings raise a question about the best serum ferritin threshold to use when seeing a child with evidence of sleep restlessness, in particular with elevated" periodic limb movement index, Ms. Connor said. "While many children may benefit from iron supplementation for these disorders, this area is worthy of further study as investigation in animals suggests that treatment of iron deficiency with high-dose iron supplementation in early development may differentially affect the development of the brain."
Ms. Connor, a student in the biomedical research program at the University of Michigan, Ann Arbor, and her colleagues conducted a review of 537 children aged 12 months to 18 years who were referred to the University of Michigan pediatric sleep clinic. In this cohort (mean age was 8.9 years; 62% were male), a median serum ferritin level of 23.6 mcg/L was linked with polysomnographic measures of periodic limb movement index (PLMI) per hour of total sleep time of 5 or more, while a median level of 30 mcg/L was linked with PLMI less than 5. About 26% of the subjects had a PLMI of 5 or more.
"There was a significant association between serum ferritin and periodic limb movement index such that, for every 10-mcg/L increase in serum ferritin, it decreased the odds of having an elevated PLMI by 11%," Ms. Connor said. Boys, younger patients, those with lower serum ferritin levels, and those with a shorter time between hematology and polysomnography had significantly increased odds of a PLMI of 5 or more. Only 19% of patients had a serum ferritin above 50 mcg/L, while 50% had below 30 mcg/L.
"The cutoff of 50 is very sensitive, giving few false negatives, but not very specific, whereas a lower cutoff improves specificity," Ms. Connor said.
Studies are needed to assess the link between iron status and sleep measures in a general pediatric population and to determine the best iron dose, timing, and method of delivery, she said.