Sleep spindles in midday naps enhance learning in preschool children
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Investigators from the University of Massachusetts sought to determine the impact of midday naps on learning and memory in preschool children. Changes in performance on a visuospatial task were measured in children recruited from preschool classrooms. Inclusion criteria included normal vision, no history of a sleep disorder, and completing the test task without reaching 100% performance at the first assessment. Learning for the visuospatial task occurred in the morning, when children were shown pictures of nouns (eg, umbrella, cat) arranged in specific squares on a grid. The grid was then hidden and the child was shown a picture of 1 noun on a separate screen and asked to point to where it had appeared on the grid. The child was given feedback about the correctness of their response, and the task was repeated until the child had an accuracy of at least 75% to ensure encoding of the information. Recall accuracy was evaluated shortly following encoding (immediate recall), in the afternoon after the usual naptime (delayed recall), and the following morning (24-hour recall). A crossover design was used so that each child experienced the learning and assessments twice – once following a nap and once after remaining awake during naptime. The 2 assessments were separated by 1 to 3 weeks. For each child, differences in accuracy between immediate recall and either delayed or 24-hour recall were calculated. These differences were then compared in each child when she/he had either napped or stayed awake. Caregivers were asked about usual napping habits in study children. Separate analyses were done on the subgroups of children who habitually napped, defined as napping >5 days/week, and those who did not usually nap (defined as <2 days/week).

A total of 77 children, ages 36 to 67 months, were enrolled in the study; 40 (31 females, mean age 49.8 months) completed both conditions and were included in the final analysis. Immediate recall was similar at around 75% when children were tested prior to having a nap or staying awake (P = .7). In contrast, delayed recall and 24-hour recall accuracy were significantly greater following a nap than when the nap was eliminated (P = .007). Children who habitually napped (n = 17) had a decline in recall accuracy of approximately 15% (P = .021) when kept awake, whereas those characterized as not usually napping (n = 10) did not demonstrate significant differences between the wake and nap conditions.

The authors conclude that midday naps support learning in preschool children who habitually nap. Furthermore, these effects are not ameliorated by subsequent overnight sleep.

Dr Nalven has disclosed that her husband works for Therapeutics MD (pharmaceutical) in a therapeutic area unrelated to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device....

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