Circadian rhythms in sleep and wakefulness and in salivary melatonin and cortisol concentrations in mothers of term and preterm infants

Abstract

We compared the effects of the demands of term and preterm infants on the daily rhythms of sleep and wakefulness and salivary melatonin and cortisol concentrations in mothers for up to 5 months after either birth (term group) or arrival of the infant home (preterm group). Although there were relatively small differences between the term and preterm groups in the daily patterns of infant sleep-wake behavior, there were more marked differences in the maternal sleep-wake parameters. During the first 8 weeks after the arrival of the infant home, the mothers of preterm infants had significantly less time asleep and fewer sleep bouts per 24 hours than did the mothers of term infants. The mothers of preterm infants spent a significantly longer proportion of each night awake (30-40%) for the first 8 weeks than did the mothers of the term infants (20-30%). There was also a significant difference between the term and preterm groups in the effect of time of day on maternal salivary melatonin concentrations. In the term group, maternal melatonin concentrations were higher at night (10 p.m.-6 a.m.) than at any other time of day. In contrast, in the preterm group maternal melatonin concentrations between 10 p.m. and 6 a.m. were only higher than those measured between 6 a.m. and 2 p.m. Salivary cortisol concentrations were significantly higher in the mothers of preterm infants than in the mothers of term infants throughout the 10-week study period, but the peak in salivary cortisol concentrations occurred between 2 a.m. and 10 a.m. in both the term and preterm groups. It is clear that mothers of preterm infants are exposed to a period of greater physiological disruption than the mothers of term infants and that the causes and consequences of such disruption require further attention.