Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Randomized Controlled Trial
. 2022 Jun;8(3):270-276.
doi: 10.1016/j.sleh.2022.01.003. Epub 2022 Apr 21.

Earlier bedtimes and more sleep displace sedentary behavior but not moderate-to-vigorous physical activity in adolescents

Kendra N Krietsch  1 , Kara M Duraccio  2 , Nanhua Zhang  3 , Brian E Saelens  4 , Taylor Howarth  5 , Angela Combs  6 , Dean W Beebe  7
Affiliations
Randomized Controlled Trial

Earlier bedtimes and more sleep displace sedentary behavior but not moderate-to-vigorous physical activity in adolescents

Kendra N Krietsch et al. Sleep Health. 2022 Jun.

Abstract

Objectives: Correlational models suggest increased cardiometabolic risk when sleep replaces moderate-to-vigorous (but not sedentary or light) physical activity. This study tested which activity ranges are impacted by experimentally altering adolescents' bedtime.

Method: Adolescents completed a 3-week within-subjects crossover experiment with 5 nights of late bedtimes and 5 nights early bedtimes (6.5- and 9.5-hours sleep opportunity, respectively). Experimental condition order was randomized. Waketimes were held constant throughout to mimic school start times. Sleep and physical activity occurred in the natural environments, with lab appointments following each 5-day condition. Waist-worn accelerometers measured physical activity and sedentary behavior. Wrist-worn actigraphs confirmed sleep condition adherence. Wilcoxon tests and linear mixed effects models compared waking activity levels between conditions and across time.

Results: Ninety healthy adolescents (14-17 years) completed the study. When in the early (vs. late) bedtime condition, adolescents fell asleep 1.96 hours earlier (SD = 1.08, d = 1.82, p < .0001) and slept 1.49 hours more (SD = 1.01, d = 1.74, p < .0001). They spent 1.68 and 0.32 fewer hours in sedentary behavior (SD = 1.67, d = 1.0, p < .0001) and light physical activity (SD = 0.87, d = 0.37, p = .0005), respectively. This pattern was reflected in increased proportion of waking hours spent in sedentary and light activity. Absolute and proportion of moderate-to-vigorous physical activity did not differ between conditions (d = 0.02, p = .89; d = 0.14, p = .05, respectively).

Conclusions: Inducing earlier bedtimes (allowing for healthy sleep opportunity) did not affect moderate-to-vigorous physical activity. Alternatively, later bedtimes (allowing for ≤ 6.5 hours of sleep opportunity, mimicking common adolescent school night sleep) increased sedentary behavior. Results are reassuring for the benefits of earlier bedtimes.

Keywords: Health promotion; Moderate to vigorous physical activity; Obesity; Pediatric; Sedentary activity; Sleep duration.

PubMed Disclaimer

Conflict of interest statement

Declaration of conflicts of interest

The study authors have no conflicts of interest to report.

Figures

Figure 1.
Figure 1.
Sleep manipulation design. Note: Wake times were held constant throughout the entire study procedures, set at a time that would allow adolescents to attend 8 AM Saturday study visits. Most (75%) of wake times fell between 6:30 AM and 7:30 AM for both early and late bedtime conditions.
Figure 2.
Figure 2.
Accumulation of time spent in various activity levels in late vs. early bedtime. Note: Early bedtime = bedtime set to allow 9.5 hours/night sleep opportunity for 5 nights; Late bedtime = bedtime set to allow 6.5 hours/night sleep opportunity for 5 nights; Sedentary = sedentary behavior (0–100 movement counts/minute); Light = light physical activity (101–2295 counts/minute); Moderate-to-vigorous physical activity (≥ 2296 counts/minute). *p < .05 comparing values between late bedtime and early bedtime conditions during the 10 PM-12 AM bin only
See this image and copyright information in PMC

References

    1. Wheaton AG, Everett Jones Sherry, Cooper Adina, Croft Janet. Short sleep duration among middle school and high school students - United States, 2015. MMWR Morb Mortal Wkly Rep. 2018;67(3):85–90. - PMC - PubMed
    1. Miller MA, Kruisbrink Marlot, Wallace Joanne, Ji Chen, Cappuccio Francesco. Sleep duration and incidence of obesity in infants, children, and adolescents: a systematic review and meta-analysis of prospective studies. Sleep. 2018;41(4). p. zsy018. - PubMed
    1. Hart CN, Hawley NL, Wing RR. Development of a behavioral sleep intervention as a novel approach for pediatric obesity in school-aged children. Sleep Med Clin. 2016;11(4):515–523. - PMC - PubMed
    1. Arteaga SS, Esposito Layla, Osganian Stavroula, Pratt Charlotte, Reedy Jill, Young-Hyman Deborah. Childhood obesity research at the NIH: Efforts, gaps, and opportunities. Transl Behav Med. 2018;8(6):962–967. - PMC - PubMed
    1. Wheaton AG, Ferro GA, Croft JB. School start times for middle school and high school students - United States, 2011–12 School Year. MMWR Morb Mortal Wkly Rep. 2015;64(30):809–813. - PMC - PubMed

Publication types