The Development of Circadian Rhythms in Human Infants

Melatonin is widely used for sleep promotion in the context of paediatric medicine,
especially in children with developmental delay (Dodge & Wilson, 2001, Phillips &
Appleton, 2004) but with limited evidence of its effectiveness and efficacy.
Melatonin use in children and adolescents warrants further investigation, not only in
this context but in light of this study‟s findings, also in the infant group. This will
allow a fuller understanding of its role in developmental physiology and potential
therapeutic uses which may have broad and far reaching applications and
implications.
11.3 Pattern of cortisol secretion and how it relates to age and
temperature maturation
Is there a pattern of change with age of cortisol secretion in human infants in the
postnatal period and how does it relate the change to development of body
temperature?
Infants included in this study had urine samples collected by their parents, during the
period of monitoring, for cortisol estimation. This was to determine the pattern of
cortisol secretion in the group, with particular interest in the emergence of a diurnal
rhythm.
Using a comparable definition to that used in melatonin analysis, the emergence of a
diurnal rhythm was taken as the week more than fifty percent of total cortisol was
produced during the day (Sivan et al 2001). Day time cortisol secretion exceeded
night time secretion from 6 weeks of age onwards (see results 6.1.2). The percentage
day/total cortisol was on average sixty percent for all weeks measured. Similar
caveats apply for the interpretation of this section of the results, as for melatonin (see
discussion section 11.2). The graphs (figures 6.1, 6.2, 6.4 and 6.5) as well as the data
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