The Development of Circadian Rhythms in Human Infants

A total of 138 actigraphy measurements were taken from 35 infants. On average each
infant had (SD) 2.67 (1.338) measurements (range 1 to 6). Three actigram readings
were discarded due to incomplete data collection therefore only 135 actigrams were
included in analysis. Six nights of sleep were not captured using actigraphy due to
unavailability of equipment.
On every given night of monitoring, there was variation in the times each infant was
put to bed (determined by infant care routine and family schedule), fell asleep and
woke. Fixed bed times were kept by three families following a Gina Ford infant care
and sleep schedule. During the analysis of the actigraphy data using the accompanying
software bed time and get up times were inputted by the operator from sleep diary
entries completed by the mothers for each night of sleep monitored. The actigraphy
software used a default sleep start and sleep end time of 23:00 and 8:00. The sleep
start and end times therefore were manually altered using sleep diary entry. This was
related to time of lights out using data from light sensor and the height of the
actigraphy trace. To allow compete data capture and allow for a sufficient margin for
error the analysis window was set to 60 minutes before and 60 minutes after bed and
get up time.
Details of infant sleeping arrangements (bedding, tog value, location, and sleep
position) were recorded and validated by direct observation by a trained researcher.
The mother self reported on infants sleep pattern using a standardised sleep diary.
Infant sleep was monitored on average from 5 to 18 weeks of age.
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