Napping and memory consolidation in early childhood: A systematic review and meta-analysis.

A growing body of evidence suggests that napping improves memory consolidation. This systematic review and meta-analysis aimed to examine the effects of napping on declarative memory consolidation in early childhood. Databases search identified 32 studies for inclusion in the systematic review, of which 27 were eligible for the meta-analysis. Effect sizes were evaluated for all samples together before separately assessing their effects on age categories ([infants and toddlers], and preschoolers) and tasks (language learning, emotional memories and imitation paradigm). Then, whether nap effects were moderated by study features such as age, nap total sleep time (TST), nap start time, habituality, and study design was evaluated. There was a positive effect of naps on declarative memory (N = 27, k = 67, Hedges' g = 0.35 (small), t (66) = 4.7, 95 % CI = 0.2 to 0.5, p < 0.0001). Notably, this effect remained significant in preschool-aged children, where naps yielded a moderate effect size (N = 10, k = 35, Hedges' g = 0.60, t (34) = 4.03, 95 % CI = 0.3 to 0.9, p = 0.0003). Based on the findings of this meta-analysis, napping has beneficial effects on memory consolidation throughout early childhood, suggesting that scheduled naps, specifically at preschool age, may still facilitate the acquisition of new information. Protocol registration: CRD42023446173.