The Development of Circadian Rhythms in Human Infants

Summary and Future work
This study highlights that the first four months for an infant are crucial and critical to
development, maturation and adaptation to an independent life outside of the
intrauterine environment and separate from the mother. The rapidity and extent of
change may confer increased vulnerability to the infant if challenged by an external
adverse factor such as an infection.
In summary this research again showed that infants demonstrate an „abrupt‟ change in
overnight core body temperature during night time sleep which may be used as a
marker of physiological maturity, as shown previously in work by this group. There
are obvious changes in infant behaviour and physiology which occur alongside the
achievement of a diurnal temperature rhythm (patterns in melatonin secretion, sleep
consolidation and a diurnal pattern of peripheral gene expression). Changes in
cortisol secretion appear to be an early and important circadian rhythm that develops
(pre temperature maturity) which may act as a trigger or act as a catalyst or key to the
development of other circadian rhythms.
As suggested by previous work and further supported by this study, although the order
of development in general stays the same, the timing of the maturation may be
different for individuals (infants in this case). The same physiological events give rise
to physiological maturity at different ages in different babies.
Developmental periods which have been studied more extensively such as prenatal
growth and development and puberty have given clear examples of development
being ordered, sequential and universal. This study opens the door to several lines of
241