Behavioral Intervention that Extends Sleep Duration Leads to Greater Self-Control in School-Aged Children.

Self-control was measured only by caregiver report, and caregivers were not blinded to which group their child was in, so their expectations could have shaped the ratings. The authors say this themselves and call for later studies using teacher reports or objective measures. Everyone in the study slept 9.5 hours or less a night, was 8 to 11 years old, and came from a family that spoke English. The findings may not apply to other ages or to families whose main language is not English, and chronotype shifts around puberty. 11 of the 78 randomized children were left out of the analysis, 3 because their 8-week assessment came more than 12 weeks after the intervention and 6 because the activity monitor data were unusable. The chronotype questionnaire was added after the study had already started, so only 57 children have those data, and the difference between chronotype groups was not statistically significant; the authors say larger, adequately powered studies are needed. The intervention targeted sleep only and did nothing else for self-control, eating or activity, so this trial cannot say whether other kinds of support for self-regulation would work as well or better.

The text provided does not include a funding or conflict-of-interest statement, so there is nothing to report on who paid for or designed the study.

Do not read the improvement in self-control as proof the programme changed how the children behave. The caregivers who rated self-control knew whether their child was in the sleep programme or the control group, and they were not blinded. Also do not treat the larger gain seen in children with an evening preference as an established effect: that difference did not reach significance (p = 0.40), and the authors say larger studies are needed to replicate it.