Periodic limb movements in sleep and iron status in children.
OBJECTIVE
To assess potential relationships between serum iron and ferritin levels and the severity of periodic limb movement in sleep (PLMS) in a pediatric population, and to evaluate the response to supplemental iron therapy.


METHODS
A prospective study of all consecutively diagnosed children with PLMS (periodic limb movement index [periodic limb movements per hour of total sleep time, [PLMI] > 5) who underwent overnight polysomnographic evaluation. In all patients, complete blood count and serum iron and ferritin levels were obtained. Patients with serum ferritin concentrations less than 50 microg/L were prescribed iron sulfate at 3 mg/kg of elemental iron per day for 3 months. At the end of treatment, serum iron and ferritin levels and sleep studies were repeated.


METHODS
Comprehensive Sleep Medicine Center, Tulane University Health Sciences Center, and Kosair Children's Hospital Sleep Medicine and Apnea Center.


METHODS
Twenty boys and 19 girls with PLMS with a mean age of 7.5 +/- 3.1 years.


METHODS
Iron therapy.


RESULTS
Twenty-eight (71.8%) patients had ferritin levels less than 50 microg/L. There was no significant correlation between serum ferritin concentration and PLMS severity as indicated by the PLMI (r = -0.19). The PLMI in patients with serum ferritin levels less than 50 microg/L (29.9 +/- 15.5 PLM/h) was higher than in patients with serum ferritin levels greater than 50 microg/L (21.9 +/- 11.8 PLM/h); however, the difference did not achieve statistical significance (P = 0.09). In contrast, serum iron was significantly correlated with PLMI (r = -0.43, P < 0.01). Indeed, patients with serum iron concentrations less than 50 microg/dL had a higher PLMI compared to patients with serum iron concentrations greater than 50 microg/dL (42.8 +/- 18.3 PLM/h and 23.1 +/- 10.1 PLM/h, respectively; P = 0.02). Twenty-five out of the 28 PLMS patients with serum ferritin levels less than 50 microg/L received treatment with iron sulfate, and 19 (76%) responded favorably. Among the responders to iron therapy, PLMI decreased from 27.6 +/- 14.9 PLM per hour to 12.6 +/- 5.3 PLM per hour after 3 months of iron supplements (P < 0.001) and coincided with increases in serum ferritin levels (pre: 40.8 +/- 27.4 microg/L vs post: 74.1 +/- 13.0 microg/L; P < 0.001).


CONCLUSIONS
In children, the presence of PLMS is frequently associated with low serum iron and a tendency toward low serum ferritin levels. In addition, iron therapy is associated with clinical improvement in most of these patients.
Department of Pediatrics, Tulane University School of Medicine, New Orleans, Louisiana 70112, USA. nsimaka@tulane.edu
Narong
N
Simakajornboon
David
D
Gozal
Vukmir
V
Vlasic
Cindy
C
Mack
Denise
D
Sharon
Brian M
BM
McGinley
D000293:Adolescent; D018798:Anemia, Iron-Deficiency / Q000097:blood / Q000150:complications / Q000188:drug therapy; D002648:Child; D002675:Child, Preschool; D005260:Female; D005293:Ferritins / Q000097:blood / Q000172:deficiency*; D006801:Humans; D007223:Infant; D007501:Iron / Q000627:therapeutic use; D008297:Male; D020189:Nocturnal Myoclonus Syndrome / Q000209:etiology / Q000378:metabolism*; D011446:Prospective Studies; D012720:Severity of Illness Index
D005293:Ferritins; D007501:Iron