Increased sleep tendency in jaundiced infants: role of endogenous CO.

Carbon monoxide formed from the breakdown of heme to bilirubin is produced at a rate equal to the rate of bilirubin synthesis. During long-term clinical experiences we have observed that jaundiced newborns tend to sleep more than the unjaundiced ones. There is no clear evidence about the role of endogenous CO in sleep physiology, but increased CO production in jaundiced newborns probably plays role in increased sleep state due to the regulatory effects on sleep circadian rhythm and REM-sleep, via cholinergic system activation.