Table 1.

Summary of reviewed studies for sleep and cognitive development

Study	Country	Design	Sleep variable	Method of sleep assessment	Dependent variables	Subjects	Control group	Sleep measured at age	Key findings
Bernier et al37	Canada	Longitudinal association study	24-hour sleep cycle	Sleep logs	Primary outcome: WPPSI (48 months) Additional outcome: battery of executive functioning tasks (24 months) and general cognitive ability measured with Mental Development Index of Bayley Scales of Infant Development (12 months)	65	None	12 months	Higher proportions of night sleep at 12 months predict better executive functioning in terms of WPPSI Matrix Reasoning at 48 months No association between total sleep duration and general cognitive ability
Bernier et al38	Canada	Longitudinal association study	Daytime and nighttime sleep patterns	Sleep logs	Primary outcome: executive functioning, measured with working memory task (18 months), and working memory, inhibitory control, and set shifting (26 months) Other outcomes: general cognitive ability measured with Mental Development Index of Bayley Scales of Infant Development	60	None	12–13 and 18 months	Higher proportions of night sleep (out of total sleep) at 12–13 and 18 months predicted better executive functioning at 18 and 26 months
Gibson et al35	New Zealand	Cross-sectional association study	Sleep efficiency and 24-hour sleep cycle	Actigraphy, sleep logs, Brief Infant Sleep Questionnaire	Primary outcome: general cognitive development measured with the Ages and Stages Questionnaire and BMI Additional outcomes: motor development measured with Ages and Stages Questionnaire	52	None	11–13 months	Sleep efficiency and longer proportions of night sleep were significantly associated with better cognitive problem-solving skills
Gómez et al26	USA	Cross-sectional experimental study	Daytime nap	Actigraphy and sleep logs	Primary outcome: language learning by general grammatical patterns of artificial language by recording looking behavior	16 (nap)	16: nap control and 16: no-nap control	15 months	Infants who napped had enhanced abstraction of grammatical relations on test trial at a 4-hour delay test
Horváth et al28	UK	Cross-sectional experimental study	Daytime nap	Actiwatch	Language learning task of familiar and novel object–pseudoword pairs (by measuring looking behavior)	14 (nap)	17 (no-nap)	16 months	Infants who napped after training task had better object–word pair learning in test trial than children who did not nap
Hupbach et al27	USA	Cross-sectional experimental study	Daytime nap	Actigraphy and sleep logs	Language learning by general grammatical patterns of artificial language by recording looking behavior	24 (nap)	24 (no-nap)	15 months	Infants who napped within 4 hours after training trial had enhanced abstraction of grammatical relations on test trial after 24 hours, in comparison to those who did not nap within 4 hours after training trial
Lukowski and Milojevich33	USA	Cross-sectional association study	Daytime and nighttime sleep patterns and sleep–wake behaviors	Brief Infant Sleep Questionnaire	Declarative memory and generalization measured with an elicited imitation task	25	None	10 months	Daytime naps predicted immediate recall and generalization
									Percentage of night sleep does not predict immediate recall or generalization Delayed recall was not predicted by sleep patterns or sleep behavior
Scher34	Israel	Cross-sectional association study	Sleep efficiency and sleep–wake behaviors	Actigraphy, sleep logs, and Sleep Questionnaire	Primary outcome: general cognition measured with the Mental Development Index of the Bayley Scales of Infant Development	50	None	10 months	Better sleep efficiency predicted higher Mental Development Index scores
				Additional outcome: psychomotor developmental index of the Bayley Scales of Infant Development					Greater night awakenings and activity in sleep predicted lower Mental Development Index scores
Seehagen et al25	Germany	Cross-sectional experimental study	Daytime nap	Actigraphy	Declarative memory measured with a deferred imitation paradigm		Experiment 1/experiment 2		Infants who napped after learning had better memory consolidation compared to children in the baseline condition (who were not trained on the object–action pairings) both after 4- and 24-hour delay
						40/32 (nap)	40/32: baseline and 40/32: no-nap	6 months (n = 60/48) 12 months (n= 60/48) and age-matched control group	Infants who napped after learning had better memory consolidation compared to children who did not nap after 24-hour delay

Abbreviations: WPPSI, Wechsler Preschool and Primary Scale of Intelligence; BMI, body mass index.