Abstract Study Objectives We examined the impact of a sleep extension intervention on multiple dimensions of sleep in adults with habitual short sleep duration. Methods Thirty healthy participants (14 women; aged 23.1 ± 4.5 years; BMI 22.3 ± 2.2 kg/m2 mean ± SD) with 6.5 h sleep/night completed a 2-week baseline assessment followed by a 4-week sleep extension intervention (2 h/night increased time in bed). Wrist actigraphy, at-home electroencephalography (EEG; DREEM headband), Insomnia Severity Index (ISI), Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), and daily quality/satisfaction and alertness Likert-scales quantified sleep. Results Baseline total sleep time (TST) was 5.5 ± 0.7 h. During sleep extension, actigraphy time in bed and TST increased (p .001) by 60.8 ± 46.7 and 46.6 ± 41.1 minutes, respectively, sleep onset shifted earlier (p .001) by 51.9 ± 64.5 minutes, with regularity similar to baseline. EEG showed increases (all p .05) in TST (61.8 ± 75.6 minutes), Stage N1 (5.09 ± 6.51 minutes), Stage N2 (39.54 ± 41.78 minutes), rapid eye movement sleep (13.58 ± 28.86 minutes), and wakefulness after sleep onset (4.86 ± 8.03 minutes), with a nonsignificant decrease (p = .07) in sleep efficiency (−1.38 ± 4.15%). Subjective alertness, ISI, PSQI, and ESS each improved (all p .05) during sleep extension. Conclusion Our findings help establish efficacy of sleep extension as an experimental intervention the sleep field can leverage across diverse contexts to study potential health benefits of increasing free-living TST. During sleep extension, the largest effects were observed for improved TST and ESS. Alternatively, some sleep dimensions including sleep regularity remained unchanged, highlighting a potential need for developing multi-component interventions that can improve more dimensions of sleep as both short and irregular sleep are linked with adverse health outcomes. Clinical Trials Biomarkers of Increased Free Living Sleep Time. URL: https://clinicaltrials.gov/study/NCT04214184. ClinicalTRIALS.gov ID: NCT04214184. Statement of Significance We provide a comprehensive evaluation of the effects of a free-living sleep extension intervention on multiple dimensions of sleep health in adults with habitual short sleep duration. Using multiple objective and subjective outcomes, we show that extending time in bed for 4 weeks increases total sleep time and selectively increases N1, N2, and rapid eye movement sleep, while sleep regularity and N3 sleep remain unchanged. Sleep extension also improves subjective sleepiness and sleep quality. These findings help establish sleep extension as an experimental intervention for increasing free-living sleep duration and improving specific dimensions of sleep health. Importantly, the lack of improvement in some dimensions highlights the need for multi-component interventions to address sleep health and related disease risk more fully.
Stegman et al. (Thu,) studied this question.