Investigators from the Duke-NUS Medical School, Singapore, conducted a randomized controlled trial to assess the impact of multi-night sleep restriction on retention of factual knowledge in adolescents. Healthy adolescents, 15–18 years old, were recruited for the study via online advertisements and visits to schools in Singapore. Once enrolled, participants were randomized to a sleep restricted (SR) or control group; randomization was stratified by gender. The SR group was provided 9 hours of sleep opportunity for 2 nights at baseline, followed by 5 consecutive nights when sleep opportunity was restricted to 5 hours (1:00 am–6:00 am), with a final 3 nights of 9 hours of sleep opportunity. Those in the control group were given 9 hours of sleep opportunity throughout the study period. After the fourth night of sleep restriction for the SR group (and the same day for controls), participants learned factual knowledge about arthropods during six 40-minute sessions. Prior knowledge was assessed with a pretest. Retention of the factual knowledge was assessed 30 minutes following the final learning session and again 3 days later with 120-item tests. In addition to answering each item, participants were asked to rate the confidence of each answer using a scale of “certain,” “somewhat certain,” or “guess.” A surprise test was administered to a subset of participants who returned 6 weeks following the study period for a debriefing session.
The primary study outcome was “certain memory,” defined as the difference between correct and incorrect answers on each test for which a participant was certain about the response. The percentage of correct answers on each test (overall memory) was a secondary outcome. Differences in the test scores between those in the SR and control groups were compared using ANOVA or t-tests.
Data were collected on 59 participants (29 SR and 30 control) with a mean age of 16.1 years. There was no difference between groups in pretest scores on knowledge of arthropods. However, certain memory scores were significantly lower among those in the SR group at 30 minutes (P = .014) and 3 days (P = .01) after the learning sessions; overall memory scores were also lower at 30 minutes (P = .047), but not 3 days (P = .122). Among 14 SR and 22 control participants who returned at 6 weeks, certain memory and overall memory were significantly lower for those randomized to the SR group than in controls (P = .003 and P = .005, respectively).
The authors conclude that long-term retention of factual knowledge was adversely affected by multi-night sleep restriction in adolescents.
Dr Wong has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.
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