The Development of Circadian Rhythms in Human Infants

1.2 Physiological Development in Humans
Human development occurs in a set sequence. The timing of the sequence may be
altered but in most cases the integrity of the order is always maintained and is the
same, irrespective of external factors (Falkner & Tanner 1986). Physiological state,
although preset from before birth, matures with increase in age. There are certain
periods in development when the pace of change is at its greatest, and it is then that
the developing infant is at its most vulnerable (Chamley et al, 2005, Slater & Lewis,
2002). This describes well the journey an infant undergoes in the first few postnatal
months, moving from newborn to full „adult‟ physiological maturation.
A comprehensive description of the different aspects of development was given by
Boyd and Bee (Bee & Boyd, 2007). Puberty is a period of development which
illustrates this clearly. It is a common human experience. It cannot be reversed. The
sexual development occurs in a set order, however the timing of the change can be
altered by external factors, the environment and illness.
Aspects of development change as an individual gets older (Chamley et al 2005).
Previous work by this research group has demonstrated that the majority of important
developmental physiological changes occur within the early period during months one
to four, as a continuum of those which occur in the foetal period (Lodemore et al.,
1991, Petersen et al., 1991, Jackson, 2000, Jackson et al., 2004). The main aspect of
physiology investigated in this work led by Wailoo and Petersen was the development
of changes in core body temperature during night time sleep in infancy. For the
purpose of this study we chose to concentrate on the same period of development
(first four months of life) but to investigate several aspects of development in parallel.
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