Age and sex differences in overnight sleep parameters in children and adolescents

1. OBJECTIVE

Large-scale objective studies of children’s sleep parameters (e.g., bed/wake time, sleep duration, restful/restless sleep) have been limited in size and scope. Most studies rely on caregiver-reported data over a limited time. Additionally, studies of sex differences across childhood in sleep parameters have shown mixed results. Sleep Number’s ecologically-valid study characterized overnight sleep parameters by age and sex in a large sample of children ages 5–17 over multiple nights using Sleep Number smart bed technology.

2. HIGH LEVEL STUDY SETUP

This study assessed sleep parameters in a large sample of children across a wide age range, collected over multiple nights at home using Sleep Number’s smart bed technology. Data from 22,910 individuals under the age of 18 were used in this IRB-approved study.  Analyses were conducted by age group:

• Youth (5 - 10 years): n=4,272

• Preadolescent (11 - 13 years): n=5,718

• Adolescent (14 - 17 years): n=15,970

Comparisons between sexes were made within age groups and on an annual basis, from ages 8–17.  Age groups and sexes (male and female) were compared for differences in weekly means for all sleep outcomes. Sleep outcomes included bedtime, wake time, bedtime/wake time variability, sleep duration, restful sleep duration, percent restful sleep, restless sleep duration and percent restless sleep. Data were collected from January 1, 2018 to October 30, 2021 using Sleep Number’s Sleep IQ technology, which is embedded in every smart bed. Data reflects the COVID-19 pandemic, school days, holidays and weekends.

3. RESULTS

Age groups differed significantly for all sleep outcomes, particularly sleep duration, bedtime and restful sleep duration.

• Age groups also differed significantly for wake time, percent restful sleep, bedtime/wake time variability, restless sleep duration and percent restless sleep, though to a lesser degree than sleep duration, bedtime and restful sleep duration.

• For each age group, females had significantly greater sleep duration, restful sleep duration and percent restful sleep than males.

• When compared annually, females had significantly higher percent restful sleep duration (ages 10–17), earlier bedtime (ages 11 and 14–17), and earlier waketime (ages 16–17) than males.

• For both sexes, bedtime and wake time shifted later with age.

Altered sleep patterns in children in response to changing schedules: an ecologically valid study

1. OBJECTIVE

Like adults, children may alter their sleep schedules during breaks in their normal routine. For example, recent surveys found that children aged 3–17 years went to bed later and woke up later during the COVID-19 pandemic. Changes in childhood sleep schedules have not been well characterized using objective measurements. Leveraging a large data set derived from Sleep Number smart bed users, we conducted an ecologically valid study to assess whether children’s sleep schedules changed in response to summertime school breaks or the COVID-19 pandemic, which caused many children to switch from in-person to online school.

2. HIGH LEVEL STUDY SETUP

Data from 22,910 smart bed users under the age of 18 were used in this IRB-approved study. Individuals were divided into 3 age groups: youth (5 - 10 years); preadolescent (11 - 13 years) and adolescent (14 - 17 years). Data were collected from June 1, 2019 - Aug 31, 2021. Time periods were defined as follows*:

• School (Sept - May) vs summer (June - Aug)

• Pre-COVID (Sept 1, 2019 - Feb 29, 2020) vs COVID (March 1, 2020 - May 31, 2020 and Sept 1, 2020 - March 31, 2021.

*For all analyses, only school nights (Sun - Thurs) were included

Study outcomes included bedtime, waketime, bedtime/waketime variability, sleep duration, restful sleep, percent restful sleep and percent restless sleep.

3. RESULTS

Summer breaks and pre and post-Covid periods (which likely represented a change from in-person to online school for most students) were associated with delayed bedtimes and waketimes, increases in sleep duration, and changes in restful sleep, percent restful sleep, and percent restless sleep that were significant but with small effect size.

• Summer Break

  • All age groups experienced later bedtimes and waketimes and had greater bedtime/waketime variability compared to the school year.

  • Sleep duration increased for adolescents during the summer.

  • Restful sleep did not differ significantly for any group.

  • Percent restful sleep decreased and percent restless sleep increased slightly for preadolescents and adolescents.

• COVID

  • All groups experienced later bedtimes and waketimes and had greater bedtime/waketime variability during COVID vs pre-COVID.

  • During COVID, sleep duration increased for all age groups and restful sleep increased for all age groups.

  • During COVID, percent restful sleep decreased and percent restless sleep increased in adolescents.