Objective To investigate longitudinal sleep patterns in children with autistic spectrum disorders (ASDs).

Study design Prospective longitudinal study using Avon Longitudinal Study of Parents and Children, an English cohort born in 1991–1992. Parental reports of sleep duration were collected by questionnaires at 8 time points from 6 months to 11 years. Children with an ASD diagnosis at age 11 years (n=73) were identified from health and education records.

Results From aged 30 months to 11 years old, children with ASD slept for 17–43 min less each day than contemporary controls. No significant difference in total sleep duration was found in infancy, but from 30 months of age children with ASD slept less than their peers, a difference that remained significant after adjusting for sex, ethnicity, high parity and epilepsy. The reduction in total sleep was wholly due to changes in night rather than daytime sleep duration. Night-time sleep duration was shortened by later bedtimes and earlier waking times. Frequent waking (3 or more times a night) was also evident among the children with ASD from 30 months of age. Age-specific decreases of >1SD within individuals in sleep duration across adjacent time points was a predictor of ASD between 18 months and 30 months of age (p=0.04) and from 30 months to 42 months (p=0.02).

Conclusions Sleep duration in children with ASD is reduced from 30 months of age and persists until adolescence.