Key points are not available for this paper at this time.
Abstract Introduction For many adolescents, the only practical way to lengthen sleep on school nights is an earlier bedtime. However, this can be misaligned with their circadian phase. The effects of circadian misalignment remain understudied. Here, we present preliminary findings from an ongoing experimental trial comparing sleep extension that is aligned vs. misaligned with adolescents’ circadian phase. Methods Healthy 14-18-year-olds in the bottom and top quartile of reported midsleep on non-school nights (“lark” vs “owl” chronotype) underwent a 3-week protocol with three multi-night periods at home: 8-hours/night of sleep opportunity aligned with their chronotype (Week1), 6.5-hours/night centered between chronotypes (Week2), and 9.5 hours/night randomly assigned to early bedtime or late risetime conditions (Week3). Linear mixed models compared Dim Light Melatonin Onset (DLMO, collected at the end of each week) and sleep midpoint and duration (via wrist actigraphy) across week, chronotype, and random assignment during Week3 (early vs late sleep extension). Alpha was set at .01. Results Of 68 adolescents randomized, 57 (84%) completed the protocol (Mean age=15.9, 53% female). At Week1, larks and owls markedly differed in midsleep (03:16 vs 05:38) and DLMO (21:18 vs 23:30), ps.001, with midsleep and DLMO correlating well (r=.76, p.001). By design, sleep duration markedly differed across weeks (7.7 vs 6.4 vs 8.5 hours; p.001) without any significant interactions involving chronotype or randomization. Sleep midpoint and DLMO each showed week-by-randomization interactions (ps.001) but no 3-way interactions. By design, late risetime significantly delayed midsleep in Week3 only (p.001). Week-by-week follow-up tests of the randomization effect on DLMO were non-significant. Sleep midpoint showed a week-by-chronotype interaction (p.001), with later midsleep for owls pre-randomization (ps.003), but not during Week3. Midsleep at Week3 and subsequent DLMO correlated well for adolescents who were randomized to a condition that aligned with their chronotype (r=.70, p.001), but not those randomized to a misaligned condition (r=.26, p.2). Conclusion It is feasible to experimentally induce sleep patterns that meet recommendations for healthy sleep duration but are aligned or misaligned with individual adolescents’ circadian phase. We will use this protocol to study the effect of circadian misalignment on health outcomes. Support (if any) US National Institutes of Health (R01HL147915)
Beebe et al. (Sat,) studied this question.