The Effects of Hyperbilirubinemia on Sleep-Spindle Characteristics in Infants

Abstract

The purpose of this study is to investigate the effect of hyperbilirubinemia on sleep-spindle characteristics. Rhythmic activities, such as sleep spindles, may be abolished by hyperbilirubinemia. Electroencephalogram records were taken from 15 infants with hyperbilirubinemia and 18 healthy infants at the 12th week after birth. Sleep spindles of the 2 groups were compared according to location, density, duration, amplitude, frequency, asynchrony, and asymmetry. In the study and control groups, the density of the spindles was found to be 76.9 +/- 23.7 and 105.2 +/- 33.9, respectively, in a 1-hour non-rapid eye movement sleep period. The mean durations of the sleep spindles in the study and control groups were found to be 4105 +/- 802 milliseconds and 5162 +/- 1075 milliseconds, respectively. There was not any difference between the groups according to the amplitude and asymmetry. However, there was a significant difference between the 2 groups in the frequency of spindles. The mean frequency was found to be 12.5 +/- 0.6 Hz in the study group and 13.2 +/- 0.9 in the control group. The percentage of asynchronous spindles was higher in the study group than in the control group. There was a significant negative correlation between the bilirubin levels during the newborn period and density, duration, and frequency of spindles. However, there was a significantly positive correlation between the bilirubin levels and percentage of asynchronous spindles. There was a significant negative correlation between the duration of hyperbilirubinemia and spindleamplitude. We suggest that studies on the critical maturation periods of sleep-spindle patterns might provide a sensitive tool for early diagnosis of neurophysiologic brain alterations during the first trimester of life in a population of at-risk children, such as jaundiced infants.