A study of 75 parents and infants conducted in New Zealand.
Objective - to determine when infants start 'sleeping through the night' based on 3 different criteria for 'sleeping through'.
Summary - A prospective longitudinal design was used with repeated measures from 1 to 12 months of age. Data were collected via sleep diaries filled in by parents for 6 days/nights monthly over 12 months.
Sleeping through the night was assessed against 3 criteria:
- Criterion 1: sleeping uninterrupted from 24:00 to 05:00 hours (from Moore and Ucko);
- Criterion 2: the 8-hour criterion, sleeping uninterrupted for 8 hours minimum between sleep onset and time awake in the morning;
- Criterion 3: the family-congruent criterion, sleeping uninterrupted from 22:00 to 06:00 hours." (p1083)
- At 3 months 58% of infants met criterion 1
- At 4 months 58% met criterion 2
- At 5 months 53% met criterion 3
Henderson et al concluded that criterion 3 should be used by clinicians to define "sleeping through the night" for infants from 4 months old as it is "met by 50% of infants at 5 months of age, is congruent with family sleep patterns, and falls within typical sleep times" (p1086).
Despite the fact that by 12 months 27% of infants still did not meet criterion 3, Henderson et al recommend that "interventions intended to prevent infant sleep difficulties" be implemented in the first 3 months of life. Although Henderson et al may have made some contribution to defining a socially relevant meaning of "sleeping through the night", the relevance of their inferences about the development of normal sleep consolidation - on any of their three criteria - is limited by lack of data on either infant sleep location (e.g. co-sleeping, bed-sharing, solitary) or infant feeding method (breast milk or formula), both of which are known to have a profound impact on real and perceived sleep duration.