A longitudinal follow-up study of young children's sleep patterns using a developmental classification system.

Sixty-eight families participated in a longitudinal study that included video observations of sleep during the 1st year of life and annual follow-up phone interviews until the children were 4 years of age. Results revealed that approximately 19% of children have a sleep problem at 2 years of age, defined either by research criteria or parental report, and that sleep problems diminished over time. Approximately 25% of children were reported to be cosleeping at each follow-up interview, but only a third of the parents reported this behavior to be problematic. A subgroup of infants (33%), who were considered stable, non-self-soothers in the 1st year, were more likely to have a sleep onset problem and be cosleeping at the 2-year follow-up assessment.