Accurate knowledge of sleep patterns in children and adolescents is helpful in assessing sleep complaints, especially if parents expect their children to spend more time in bed than they actually need. Iglowstein and colleagues conducted a study to calculate percentile curves for total sleep duration per 24 hours from early infancy to late adolescence.

A total of 493 subjects were followed using structured interviews at one, three, six, nine, 12, 18, and 24 months after birth, and annually thereafter until 16 years of age. Total sleep duration decreased from an average of 14.2 hours at six months to an average of 8.1 hours at 16 years. Consolidation of nocturnal sleep occurred during the first 12 months after birth, with an increase in nighttime sleep duration by one year of age, followed by a marked reduction in nighttime sleep duration (see Figure 1). Daytime sleep duration gradually decreased in the first years of life, with all children napping in the first 12 months. At 18 months of age, there was a significant change from two or more naps per day to only one. At three years of age, 50.4 percent of children still napped once per day (see Figure 2).

The authors note a decrease in mean total sleep time in the three birth cohorts; the decrease was most pronounced in infants and young children. Children in the study tended to be put to bed later with each cohort, while wake-up time remained the same. The authors attribute this decrease to a more liberal parental attitude toward bedtime.