zzz.— Supposed to represent the sound of snoring. A snoring sound, implying that somebody is asleep.


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 results indicate relative stability of objectively-recorded sleep durations in healthy sleepers assessed over the last half-century. Similar results were found across all age groups, in both men and women. […] These data are consistent with recent comprehensive reviews that found no consistent or compelling evidence of significant decrements in self-reported sleep duration and/or prevalence of short sleep over a similar range of years. Together, these data cast doubt on the notion of a modern epidemic of insufficient sleep. […]

The cliche of an ever-expanding 24/7 society is not well-supported by empirical evidence, at least not over the past 50 y. For example, evidence suggests that the prevalence of shift-work has remained stable at about 15-20% over this interval of years. Such data might seem counterintuitive in light of the increased number of 24-h services and businesses. However, while many of these businesses (e.g., restaurants and convenience stores) can operate all-night with just a few employees, over the past half-century there has been a dramatic shutdown of factories which once employed thousands of shift-workers. Moreover, over the past 10-20 y, protective regulations and practices which limit shift-work and sleep deprivation and/or better accommodate individual’s preferences (e.g., flex time and telecommuting), have been implemented for various occupations, including medical residents, truck drivers, and transportation workers.

It is a widely repeated hyperbole that never before in human history have we faced such challenges to our sleep. It has been hypothesized that industrialization, urbanization, and technological advances have caused us to ignore or override our natural tendency to sleep more, and we do so at great costs to our health and quality of life. […] The light bulb has been blamed for sleep loss. However, recent anthropologic studies of people in societies with little or no electricity have failed to indicate that these people sleep more than people in industrialized societies. […]

The notion of a recent epidemic of insufficient sleep, and speculation that this is a primary contributor to modern epidemics of obesity, diabetes, metabolic syndrome, etc., rests largely on the question of whether sleep duration has declined in the last few decades. Consistent with recent reviews of subjective data, this review does not support this notion, at least not in healthy sleepers. […]

Reasons for persistent assumptions about a temporal decline in societal sleep duration could include a larger number of people assessed and diagnosed with sleep disorders with the emergence of sleep medicine; greater knowledge about sleep and the risks of inadequate sleep; increased prevalence of depression; misperceptions about population norms; and persistent claims in the popular and scientific literature regarding a so-called modern epidemic of insufficient sleep.

{ Sleep Medicine Reviews | PDF }

photo { Aug. 5, 1962. Police officer points to an assortment of prescription bottles on the bedside table in Marilyn Monroe’s bedroom in Los Angeles, where she was found dead }