The Physiological Importance of Sleep and Its Impact on Brain Development in Preschool-Aged Children

Adequate sleep in the preschool period (3–6 years) is increasingly recognised as a biological requirement for optimal neurodevelopment. Insufficient sleep—whether from curtailed nocturnal duration or fragmented napping—has been linked to alterations in cortical thickness, synaptic pruning, executive-function maturation and later behavioural outcomes. The present study addresses a gap in Central Asian paediatric sleep research by (i) synthesising recent global evidence and (ii) presenting original data from an observational cohort in Tashkent, Uzbekistan. One hundred and forty-two healthy preschoolers were followed for nine months with actigraphy, polysomnography-validated home EEG caps, salivary cortisol assays and magnetic-resonance-based morphometry. Multilevel regression showed that every 30-minute nightly sleep deficit relative to the American Academy of Sleep Medicine guideline predicted a 2.3 % reduction in prefrontal cortical volume (β = -0.47, p < 0.01), attenuated spindle density and slower executive-function gains on the Dimensional Change Card Sort. Daytime naps mitigated 38 % of the structural variance. The data confirm international reports that neuroplastic processes in early childhood are sleep-dependent and suggest culturally adapted sleep-education programmes are warranted.