The great sleep recession: changes in sleep duration among US adolescents, 1991-2012

Abstract

Background: Average nightly sleep times precipitously decline from childhood through adolescence. There is increasing concern that historical shifts also occur in overall adolescent sleep time.

Methods: Data were drawn from Monitoring the Future, a yearly, nationally representative cross-sectional survey of adolescents in the United States from 1991 to 2012 (N = 272 077) representing birth cohorts from 1973 to 2000. Adolescents were asked how often they get ≥7 hours of sleep and how often they get less sleep than they should. Age-period-cohort models were estimated.

Results: Adolescent sleep generally declined over 20 years; the largest change occurred between 1991-1995 and 1996-2000. Age-period-cohort analyses indicate adolescent sleep is best described across demographic subgroups by an age effect, with sleep decreasing across adolescence, and a period effect, indicating that sleep is consistently decreasing, especially in the late 1990s and early 2000s. There was also a cohort effect among some subgroups, including male subjects, white subjects, and those in urban areas, with the earliest cohorts obtaining more sleep. Girls were less likely to report getting ≥7 hours of sleep compared with boys, as were racial/ethnic minorities, students living in urban areas, and those of low socioeconomic status (SES). However, racial/ethnic minorities and adolescents of low SES were more likely to self-report adequate sleep, compared with white subjects and those of higher SES.

Conclusions: Declines in self-reported adolescent sleep across the last 20 years are concerning. Mismatch between perceptions of adequate sleep and actual reported sleep times for racial/ethnic minorities and adolescents of low SES are additionally concerning and suggest that health education and literacy approaches may be warranted.

Keywords: Monitoring the Future; adolescence; age-period-cohort; sleep.

FIGURE 1

According to age and time period, percentage of adolescents who regularly report: A, ≥7 hours of sleep per night; and B, getting adequate sleep per night. The proportion of adolescents who regularly got ≥7 hours of sleep was defined as those who responded that the frequency with which they obtain ≥7 hours of sleep was every day or almost every day versus sometimes, rarely, or never. The proportion of adolescents who regularly get adequate sleep was defined as those who reported that they get less sleep than they should never or seldom versus sometimes, every day, or almost every day.

FIGURE 2

Age, period, and cohort effects on the probability that US adolescents regularly report ≥7 hours of sleep per night from 1991 to 2012 in nationally representative samples (N = 270 899). The cohort and period time–scale contains risk ratio estimates for the effect of cohort (far left line) and period (far right line). Thin lines indicate 95% confidence intervals. The cohort estimates were compared with a referent cohort of 1980; thus, the lines can be interpreted as the average proportion of adolescents obtaining ≥7 hours of sleep regularly, regardless of time period, compared with the average proportion in 1980. The period estimates were compared with a referent period of 1995; thus, the lines can be interpreted as the average proportion of adolescents obtaining ≥7 hours of sleep regularly in that year, regardless of cohort, compared with the average proportion in 1995.

FIGURE 3

Age, period, and cohort effects on the probability that US adolescents regularly report adequate sleep per night from 1991 to 2012 in nationally representative samples (N = 270 719). The cohort and period time–scale contains risk ratio estimates for the effect of cohort (far left line) and period (far right line). Thin lines indicate 95% confidence intervals. The cohort estimates were compared with a referent cohort of 1980; thus, the lines can be interpreted as the average proportion of adolescents obtaining adequate sleep regularly, regardless of time period, compared with the average proportion in 1980. The period estimates were compared with a referent period of 1995; thus, the lines can be interpreted as the average proportion of adolescents obtaining adequate sleep regularly in that year, regardless of cohort, compared with the average proportion in 1995.