Sleeping position and electrocortical activity in low birthweight infants

Objective: To evaluate the effects of prone and supine sleeping positions on electrocortical activity during active (AS) and quiet (QS) sleep in low birthweight infants. Design: Randomised/crossover study. Setting: Infant Physiology Laboratory at Children's Hospital of New York. Patients: Sixty three healthy, growing, low birthweight (birth weight 795–1600 g) infants, 26–37 weeks gestational age. Interventions: Six hour continuous two channel electrocortical recordings, together with minute by minute behavioural state assignment, were performed. The infants were randomly assigned to prone or supine position during the first three hours, and positions were reversed during the second three hours. Outcome measures and results: Fast Fourier transforms of electroencephalograms (EEGs) were performed each minute and the total EEG power (TP), spectral edge frequency (SEF), absolute (AP) and relative (RP) powers in five frequency bands (0.01–1.0 Hz, 1–4 Hz, 4–8 Hz, 8–12 Hz, 12–24 Hz) were computed. Mean values for TP, SEF, AP, and RP in the five frequency bands in the prone and supine positions during AS and QS were then compared. In the prone sleeping position, during AS, infants showed significantly lower TP, decreased AP in frequency bands 0.01–1.0 Hz, 4–8 Hz, 8–12 Hz, 12–24 Hz, increased RP in 1–4 Hz, and a decrease in SEF. Similar trends were observed during QS, although they did not reach statistical significance. Conclusions: The prone sleeping position promotes a shift in EEG activity towards slower frequencies. These changes in electrocortical activity may be related to mechanisms associated with decreased arousal in the prone position and, in turn, increased risk of sudden infant death syndrome.