The Development of Circadian Rhythms in Human Infants

Extension of this period of monitoring may be helpful for future studies. An
alternative is to use a completely different sleep scoring technology (portable PSG,
video behavioural observation, motion sensitive mattresses etc. – see introduction)
which will allow fuller sleep staging.
Actigraphy is thought to be a valid tool in contributing to the assessment of sleep,
including in infants. However it does have limitations, in that it measures motion
rather than sleep itself and translates movement and non-movement into presumed
wakefulness and rest. In an adult this may be easier to interpret. In the absence of
simultaneous video records, it was difficult to extract movement artefact, for example
if the infant was being rocked to sleep. It is difficult with absolute certainty to
differentiate whether an infant was actually asleep or awake. For these reasons it may
overestimate or underestimate sleep. However in this data set there was high
agreement between the actigraphy and sleep diary entries. Future work comparing
sleep diaries, actigraphy and more complex methods of measuring infant sleep (see
introduction 1.8.4) is warranted.
Buccal swabs for peripheral gene estimation
This was novel work. There are no previous studies investigating longitudinal gene
expression in human infants over the first four postnatal months concomitantly with
physiological development.
Traditionally molecular biological and genetic studies have taken „snap shot‟ views of
gene expression at any given time either from central or peripheral tissue; or rhythms
were monitored for several days at a maximum (Brown et al., 2008) and much of this
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