Has adult sleep duration declined over the last 50+ years?

Abstract

The common assumption that population sleep duration has declined in the past few decades has not been supported by recent reviews, which have been limited to self-reported data. The aim of this review was to assess whether there has been a reduction in objectively recorded sleep duration over the last 50+ years. The literature was searched for studies published from 1960 to 2013, which assessed objective sleep duration (total sleep time (TST)) in healthy normal-sleeping adults. The search found 168 studies that met inclusion criteria, with 257 data points representing 6052 individuals ages 18-88 y. Data were assessed by comparing the regression lines of age vs. TST in studies conducted between 1960 and 1989 vs. 1990-2013. Weighted regression analyses assessed the association of year of study with age-adjusted TST across all data points. Regression analyses also assessed the association of year of study with TST separately for 10-y age categories (e.g., ages 18-27 y), and separately for polysomnographic and actigraphic data, and for studies involving a fixed sleep schedule and participants' customary sleep schedules. Analyses revealed no significant association of sleep duration with study year. The results are consistent with recent reviews of subjective data, which have challenged the notion of a modern epidemic of insufficient sleep.

Keywords: Actigraphy; Normal sleeper; Polysomnography.

Figure 1

Association of mean age of participants with total sleep time (min) for studies conducted between 1960–1989 (open circles) and 1990–2013 (closed circles).

Figure 2

Association of year of study with age-adjusted total sleep time (min) for all data points. The regression line and 95% confidence intervals are displayed.

Figure 3

Association of year of study with total sleep time (with regression line and 95% confidence intervals) for participants ages 18–27 years (a), 28–37 years (b), 38–47 years (c), 48–57 years (d), 58–67 years (e), 68–77 years (f), and ≥78 years (g).

Figure 4

Association of year of study with age-adjusted total sleep time (min) for polysomnographic data (a) and actigraphic data (b). The regression line and 95% confidence intervals are displayed.

Figure 5

Association of year of study with age-adjusted total sleep time (min) for women subjects only. The regression line and 95% confidence intervals are displayed.

Figure 6

Association of year of study with age-adjusted total sleep time (min) for studies in which subjects followed their usual sleep schedule (a), and for studies in which subjects followed a fixed sleep schedule of 470–480 min (b). The regression line and 95% confidence intervals are displayed.