Shorter sleep duration is associated with reduced cognitive development at two years of age

Both short sleep duration and sleep-disordered breathing (SDB) are associated with poor neurocognitive development. However, the co-contributions of short sleep duration and SDB on neurodevelopment in pre-school children are relatively unknown. We assessed both sleep duration and SDB by quarterly questionnaire from three months to two years of age among Canadian Healthy Infant Longitudinal Development (CHILD) birth cohort participants. Group-based modeling determined trajectories of total, daytime, and nighttime sleep duration and SDB. Linear regression was used to assess the impact of sleep duration and SDB trajectories on cognitive (primary outcome) and language (secondary) development at two years of age as assessed by the Bayley Scale of Infant Development (BSID-III) (mean 100; standard deviation of 15). Of the 822 CHILD Edmonton participants, 703 (86%) were still enrolled at two years of age with 593 having BSID-III data at two years of age. Trajectory analysis identified four total sleep durations phenotypes [short sleepers (17.9%), decline to short sleepers (21.1%), intermediate sleepers (36.9%) and long sleepers (24.1%)]. Compared to children with intermediate sleep durations, short sleepers had a 5.2-point lower cognitive development score at two years of age [standard error (SE) 1.7; p = 0.002]. Nocturnal sleep duration, compared to daytime sleep duration had the greatest effect on cognitive development. We also identified three SDB symptom trajectories [early-onset SDB (15.7%), late-onset SDB (14.2%), and persistent SDB (5.3%)] and 79.5% of children had no SDB symptoms. Children with persistent SDB also had a 5.3-point lower language score (SE 2.7; p = 0.05) compared to children with no SDB. SDB trajectories were not associated with cognitive development. In a population-representative birth cohort study, both short sleep duration and SDB were associated with adverse neurodevelopment at two years of age. Children with short nighttime sleep duration had lowered cognitive and language scores and children with persistent SDB also had lower language scores. •Four total sleep duration trajectories were identified at two years of age: At one year short sleepers (17.9%) slept 12.0 h per day, at one year decline to short (21.1%) slept 12.6 h per day at one year, intermediate sleepers (36.9%) slept 13.9 h and long sleepers (24.1%) slept 14.7 h at one year.•Short sleepers had lower cognitive development and language scores at two years of age compared to