In search of lost sleep: Secular trends in the sleep time of school-aged children and adolescents

a Health and Use of Time (HUT) Group, University of South Australia, GPO Box 2471, Adelaide SA 5000, Australiab Sansom Institute for Health Research, University of South Australia, GPO Box 2471, Adelaide SA 5000, Australiac School of Health Sciences, University of South Australia, GPO Box 2471, Adelaide SA 5000, AustraliaReceived 7 January 2011. Revised 18 March 2011. Accepted 18 March 2011. Available online 25 May 2011.View full text Sleep deficits are associated with a wide range of detrimental physical and mental health outcomes. There is concern that children are not getting enough sleep, and that sleep duration has been declining. However, evidence is sparse.

A systematic review of world literature was conducted to locate studies reporting the sleep duration of children aged 5–18 years. Monte Carlo simulation was used to generate pseudodata from summary data, which were combined with raw data and analysed by linear regression of sleep duration on year of measurement at the age × sex × day type × country level.

Data were available on 690,747 children from 20 countries, dating from 1905 to 2008. From these data, 641 regressions were derived. The sample-weighted median rate of change was -0.75 min nightly per year, indicating a decrease of more than 1 h per night over the study period. Rates of change were negative across age, sex and day type categories, but varied according to region, with Europe, the USA, Canada and Asia showing decreases and Australia, the UK and Scandinavia showing increases.

Over the last 103 years, there have been consistent rapid declines in the sleep duration of children and adolescents.

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Figures and tables from this article:

Fig. 1. PRISMA flowchart for the search.

View Within ArticleFig. 2. Funnel plots of changes in sleep duration (Y-axis, min/year) against the span of years for each regression, and the total sample size for each regression (X-axes). The dashed line is the sample-weighted median rate of change (-0.75 min/year).

View Within ArticleFig. 3. Box plots showing sample-weighted rates of change for age (Fig. 3a), sex (Fig. 3b) and day type (Fig. 3c) sub-groups. The dashed line is the sample-weighted median rate of change (-0.75 min/year). k = number of regressions assessed; SD = standard deviation; IQR = interquartile range.

View Within ArticleFig. 4. Box plots showing sample-weighted rates of change for different regions. The dashed line is the sample-weighted median rate of change (-0.75 min/year). k = number of regressions assessed; SD = standard deviation; IQR = interquartile range.

View Within ArticleFig. 5. Box plots showing sample-weighted rates of change for different year periods. The dashed line is the sample-weighted median rate of change (-0.75 min/year). k = number of regressions assessed; SD = standard deviation; IQR = interquartile range.

View Within ArticleTable 1. Search strategy used for each database.

View Within ArticleTable 2. Rates of change (minutes per day per year) in sleep duration according to sex, age, day type and geographical location.

Significant differences were found across age groups (with the exception of 13–15 and 16–18 year-old age categories), sexes, regions and between different day types (P < 0.05).k = number of regressions assessed; n = sample size; SD = standard deviation; IQR = interquartile range.

View Within ArticleCopyright © 2011 Elsevier Ltd. All rights reserved.

prs.rt('data_end');

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Secular trends in adult sleep duration: A systematic review

Little evidence exists to support the common assertion that adult sleep duration has declined. We investigated secular trends in sleep duration over the past 40 years through a systematic review.

Systematic search of 5 electronic databases was conducted to identify repeat cross-sectional studies of sleep duration in community-dwelling adults using comparable sampling frames and measures over time. We also attempted to access unpublished or semi-published data sources in the form of government reports, theses and conference proceedings. No studies were excluded based on language or publication date. The search identified 278 potential reports, from which twelve relevant studies were identified for review.

The 12 studies described data from 15 countries from the 1960s until the 2000s. Self-reported average sleep duration of adults had increased in 7 countries: Bulgaria, Poland, Canada, France, Britain, Korea and the Netherlands (range: 0.1–1.7 min per night each year) and had decreased in 6 countries: Japan, Russia, Finland, Germany, Belgium and Austria (range: 0.1–0.6 min per night each year). Inconsistent results were found for the United States and Sweden.

There has not been a consistent decrease in the self-reported sleep duration of adults from the 1960s to 2000s. However, it is unclear whether the proportions of very short and very long sleepers have increased over the same period, which may be of greater relevance for public health.

Table 1. Literature search strategy and number of results for each database.

View Within ArticleTable 2. Summary of included results by country (some studies have multiple results).

View Within ArticleCopyright © 2011 Elsevier Ltd. All rights reserved.

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