Feb. 13, 2012 -- Kids don't get the recommended amount of sleep -- and they never have.
That's the conclusion of Australian researchers who tracked changes in sleep recommendations, and what was known about actual sleep time, over more than a century.
The rate of change varied with age, but recommended sleep consistently fell and the changes were significant for eight ages: Infants as well as children ages 4 to 8, 14 and 15.
At the same time, actual sleep also fell, declining by about 0.73 minutes per year over time.
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A systematic review of the literature revealed that, since 1897, sleep recommendations for children of all ages have consistently exceeded what was known about actual sleep time, according to Lisa Anne Matricciani and colleagues at the University of South Australia in Adelaide.
In addition, both have also consistently fallen, almost in lockstep, over the years, Matricciani and colleagues reported online and in the March issue of Pediatrics.
The issue has been a matter of concern since the 19th century with observers worried that the stimulation of modern living would overtax children, the researchers noted.
The stimulation itself was usually blamed on whatever new technology was current, from radio and reading to television and the Internet.
On the other hand, those making the recommendations were consistent in admitting they had little or no evidence on which to base their suggestions, Matricciani and colleagues pointed out.
Their literature search turned up 28 studies that made sleep recommendations, and 218 that offered self- and proxy-reported sleep duration for children of various ages.
The analysis showed that, on average, recommended sleep fell about 0.71 minutes per year, or about 70 minutes over the course of the 20th century, Matricciani and colleagues found.
For 173 of some 360 recommended sleep durations, matching data were available on actual sleep. In 144 of those (83 percent) of the comparisons, recommended sleep exceeded actual sleep, with an average difference of 37 minutes.
The researchers found that recommended sleep duration was almost always higher than actual sleep duration "as if children always needed extra sleep, no matter how much they were actually getting."
A limitation of the study was that in this review, sleep duration was based on reports, rather than on objective measures such as actigraphy and polysomnography.
But those approaches have only been developed recently, are expensive and time-consuming, and have usually been applied only at the individual level, the authors noted.
Although lack of sleep has been associated with a range of adverse consequences, Matricciani and colleagues argued, there is still little understanding of dose-response effects or even the mechanisms that might lead to negative outcomes.