Michelle Lampl from Emory University and Michael Johnson from the University of Virginia Health System have documented something we all suspected was true: infants sleep more just before they grow.
The researchers compared daily sleep patterns in 23 babies for up to seventeen months. Rather than relying on parental recall, the scientists asked the parents to record sleep onset and waking in real time, as well as keeping notes on infant feeding and illness. Periods of longer total sleep time occurred just before increases in weight, body-fat composition and length.
Interestingly, baby boys tended to increase the lengths of their normal sleep periods, whereas baby girls tended to add more naps. However, it was the total increase in sleep hours that predicted the growth spurts.