The Development of Circadian Rhythms in Human Infants

Considering only those weeks of measurement where at least four consecutive
samples were taken, the 22 infants with any peripheral clock gene marker measured
were sampled on average during 4.2 separate weeks, and during each week at an
average 6.6 time points.
At the time the study was set up, sampling times for collection of buccal swabs were
selected as follows - 18:00 hours, 12:00 midnight, 06:00 hours, 12:00 midday.
Mothers kept to these times as closely as possible. However to encourage maximum
participation and compliance with the study protocol, mothers were permitted to alter
collection times to fit around their family schedule on that day. The aim was to
minimise disruption to the household routine. No adjustments were made to infant
care practice for light exposure (Lux), routine, meal times or sleep times.
The infants ranged from 5 to 18 weeks of age during the study.
When the initial study protocol was devised, the genes of interest selected for
investigation in the study were Rev-er-beta and PER2 which are central circadian
clock genes. Due to the problems with RNA yield, and the use of very technically
challenging procedures, compounded by the high risk of sample contamination, the
original central clock genes of interest Rev and PER2 could not be isolated. Multiple
adjustments to protocol and trials of several primers and techniques had to be
undertaken before any data were obtained.
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