Changes in children's sleep domains between 2 and 3 years of age: the Ulm SPATZ Health Study.

OBJECTIVE: There is growing interest in the link between sleep habits and child health but reference values specific to toddlers as well as longitudinal data on sleep are scarce. We aimed to describe parent-reported child sleep habits and their intra-individual changes in two- to three-year-olds using data from a regional birth cohort study.

METHODS: In the Ulm SPATZ Health Study, a birth cohort study conducted at Ulm, Southern Germany, with baseline examination from April 2012 to May 2013, the German version of the Children's Sleep Habits Questionnaire (CSHQ-DE) was used longitudinally at follow-ups at two and three years (N = 615 children). Descriptive statistics including intra-individual differences between three- and two-year scores were reported, the latter using the sign test.

RESULTS: The sample-averaged total and subscale CSHQ scores differed only slightly between two and three years (max. Cohen's d = 0.39). Intra-individual comparisons of the CSHQ subscales or single items revealed congruent but also opposing changes in items belonging to the same subscale. Whereas items on bedtime resistance generally improved, sleep duration shortened with older age. With regard to sleep anxiety, we found worsening in the item 'Afraid of sleeping in the dark' in about one-fifth of our children whereas other items on this CSHQ subscale showed an opposing trend with age. A similar opposing trend was detected within the subscale on night wakings.

CONCLUSION: Our data provide initial descriptive information on sleep habits in toddlers. The high intra-individual changes, partly in opposing directions which may be masked by aggregation, indicate a need for age- and item-specific analyses.