The Development of Circadian Rhythms in Human Infants

Table 10.1 - Temporal relationship of parameters measured in 35 human infants from 5 to 18
weeks of age. Mean values for age of maturation of circadian rhythm in overnight temperature
control during sleep, evening peak in melatonin secretion, morning peak in cortisol secretion,
timing of maximum sleep efficiency and maximum peripheral clock gene expression (by
amplitude and R2 goodness of fit).
Mean age (weeks)
Cortisol Melatonin Sleep Temperature Clock gene
8.17
9.10
201
9.40
10.79
10.86
Number of infants 35 30
35 34
21
SD (weeks) 2.065 2.187 0.509 2.869 2.308
SEM (weeks) 0.349 0.399 3.012 0.492 0.504
Minimum (weeks) 6 5 6 6 7
Maximum (weeks) 16 16 16 18 16
When the week that the infant had minimum number and percentage of immobile
phases of 1 minute duration, was examined, the infants were found to have most
settled sleep period at 11.05 weeks of age (age with maximum number of immobile
minutes during night time sleep) and 11.31 weeks of age (age at which minimum
number of immobile phases during night time sleep).