Associations of sleep duration with neurocognitive development in the first 2 years of life

Abstract

The effect of sleep duration on neurocognitive development in infants and toddlers remains unclear. We aimed to investigate the relationship between sleep duration and neurocognitive development in infancy. Based on a prospective birth cohort, 2220 mother-infant pairs were enrolled in Wuhan, China, between January 2014 and October 2017. Sleep duration was evaluated at 1, 6, 12 and 24 months via parentreport questionnaires. To assess the children's neurocognitive development at 2 years old, the Bayley Scales of Infant Development of China Revision was used to assess the Mental Development Index (MDI) and Psychomotor Development Index (PDI). A group-based semiparametric mixture model was used to estimate the developmental trajectories of the total, nighttime and daytime sleep duration. The associations of sleep duration at each age and sleep duration trajectories with Mental Development Index scores and Psychomotor Development Index scores were analysed using generalized linear models. Daytime sleep duration (≥ 10.0 hr) at 1 month was associated with lower Mental Development Index scores (β = −3.55, 95% confidence interval: −6.02, −1.08) and lower Psychomotor Development Index scores (β = −2.87, 95% confidence interval: −4.94, −0.81). Nighttime sleep duration (≤ 7.0 hr) at 6 months was associated with lower Mental Development Index scores (β = −7.02, 95% confidence interval: −11.02, −3.01). Daytime sleep duration (> 4 hr) and nighttime sleep duration (< 8 hr) at 12 months were associated with lower Mental Development Index scores (β = −9.17, 95% confidence interval: −15.35, −2.98) and lower Psychomotor Development Index scores (β = −8.14, 95% confidence interval: −13.56, −2.71), respectively. In further sleep duration trajectories analyses, lower Mental Development Index scores were significantly associated with the "decreased and then increased nighttime sleepers" trajectory (β = −4.39, 95% confidence interval: −8.02, −0.76), and "long and decreased daytime sleepers" trajectory (β = −2.44, 95% confidence interval: −4.58, −0.30). These results showed that short nighttime sleep duration and long daytime sleep duration in infancy were detrimental to children's neurocognitive development.

Trajectories of reported sleep duration associate with early childhood cognitive development

“…Our finding of lower cognitive and fine motor scores on Bayley-III with the long variable day sleep trajectory (relative to the short consistent day sleep trajectory) was similar to the lower MDI scores observed by Cao et al with the “long and decreased” day sleep trajectory [ 28 ]. Longer day sleep might lead to later bedtime, poorer night sleep quality and shorter nocturnal sleep [ 41 ], hence impairing neurodevelopment.…”

“…Their findings are consistent with our findings, in that children from long and consistent total and night sleep trajectories performed better in both Bayley-III cognitive and language scales compared to children from short total and night sleep trajectories. Separately, Cao et al [ 28 ] derived 4 total-, 4 night-, and 3 day-sleep trajectories using 1–24 months sleep data from a birth cohort in China and found that a “decreased then increased” night trajectory was linked to poorer performance on the Bayley-II MDI. However, they did not observe significant differences in Bayley-II performance between the total sleep trajectory groups.…”

“…Another strength of our study is the inclusion of breastfeeding duration in our model, which is an important confounder associated with both cognition and sleep. We also add on to Cao et al [ 28 ] and Smithson et al [ 27 ] studies by following up with another cognitive test at 54 months, to examine if the cognitive and verbal/language advantage persists. We recognize that our sample size is relatively small and may require replication.…”

“…They also found that long nocturnal sleepers had higher cognitive and language scores in Bayley-III compared to short and intermediate nocturnal sleepers. Cao et al observed in a population of Chinese children that children belonging to trajectories characterized by “decreased and then increase nighttime sleepers” and “long and decreased daytime sleepers” between 1 and 24 months of age tend to have lower Bayley-II Mental Development Index (MDI) scores [ 28 ]. Apart from cognition, sleep trajectories in early childhood (0–7 years of age) had been associated with health-related quality of life, where persistent short sleepers had reportedly worse emotional, social, and physical health [ 21 ].…”