The Development of Circadian Rhythms in Human Infants

10 Results
10.1 Circadian rhythms – investigation of temporal
relationships
In this study several parameters were examined concurrently and longitudinal
measurements made, from just before 6 to 18 weeks of age, in the cohort of human
infants enrolled. The length of time each infant remained in the study was
determined by the age each infant achieved physiological maturity characterised by
the maximum fall in overnight core body temperature (Lodemore et al., 1991, Wailoo
et al., 1989). Once physiological maturity had been demonstrated, this was confirmed
by a further core body temperature reading (taken a fortnight later) if possible. The
study protocol for urine collection (for melatonin/cortisol estimation), sleep
characterisation by actigraphy and buccal cell collection (for pattern of peripheral
clock gene expression) continued till the study end point.
Definitions
The previously described definition of physiological maturation of deep overnight
body temperature with sleep has been well described (Lodemore, 1991).
Definitions encompassing age related changes in the patterns of the other parameters
(melatonin secretion and cortisol secretion, infant night time sleep and peripheral
clock gene expression) were developed during the investigation period for this study.
These definitions do not include an exact age of maturation of a robust circadian
rhythm in each area (other than for temperature maturation). This study was limited
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