The Development of Circadian Rhythms in Human Infants

predominantly affluent areas of the city and county. One study in a deprived area had
71% of mothers agree to participate from an inner city area. It should be noted that in
these earlier studies a different method of recruitment using a negative response reply.
In these studies mothers were selected from a child health records list and sent letters
of invitation to participate with a fixed visit time already prearranged. Mothers were
then expected to call the university to cancel the appointment if they did not want to
participate.
The retention rate in the Murray study was 23%. In this study it was 100%. This is
despite initial anxiety by members of various panels and committees that mothers
would not want to or be able to participate in a study of this type. Families were very
motivated and very keen to help.
The mothers who took part in the study were significantly older (maternal age SD)
than those who declined (mothers of participant infants 31.23 (1.114) years c.f.
mothers who declined study 26.84 (1.239) years) p=0.005. There is missing data from
the mothers who declined (n=3). The mothers cited lack of time, the equipment, or
partner objection as the most common reasons for declining to take part.
3.1.2 Summary of demographic data
One in three infants in the study (11/35) was resident in Leicester City centre. The
rest were recruited from the surrounding area (Leicestershire, Rutland,
Northamptonshire). The demographic data for the infants who participated in this
study are given below with special reference to infant characteristics, social class of
the family and key aspects of infant care such as method of feeding (Table 3.1).
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