You probably can’t get through a single year without reading one article or watching one news segment on TV about the detriments the lack of sleep has on people. The blame is usually cast on modern society’s fast pace of life and there being so much to do. And, in fact, sometimes a lack of sleep can be a sign or symptom of other problems (such as this article notes in teens).
The average adult gets between 7 to 7 1/2 hours of sleep per night, and the average child and teen, about 9 hours. Common wisdom suggests adults also need 8 to 9 hours a day, but there’s little empirical support for this number.
Jim Horne over at the New Scientist makes the claim that we’re not putting sleep deprivation into proper historical context and largely dismisses the wealth of scientific evidence that links sleep loss to a myriad of health and mental health issues.
Horne singles out two of the most well-known health problems associated with sleep loss — obesity and diabetes. He notes that you could offset any resulting weight gain from sleep loss by simply not eating “one bite of a muffin” per day. His argument boils down to one commonly made in research — what’s the difference between clinical significance and statistical significance in the research? He makes the case that the clinical significance (e.g., that which actually has a negative impact on your life) of most of the sleep studies done to-date is minimal, as is the associated risk of sleep loss.
Horne argues it’s all been overblown, and to some extent, he’s right. As a sleep researcher himself, he should know (and he’s made the same argument in published research, see for example Horne, 2008).
But I think Horne cherry picks the research he holds up as examples and ignores the studies that illustrate a connection between a lack of sleep to hunger, diabetes and weight issues (among a myriad of other problems). You don’t have to believe me, just ask Van Cauter and Knutson (2008) who reviewed the literature themselves and came to a similar conclusion:
Altogether, the evidence points to a possible role of decreased sleep duration in the current epidemic of obesity. […]
Consistent with the laboratory evidence, multiple epidemiologic studies have shown an association between short sleep and higher body mass index after controlling for a variety of possible confounders.
Researchers can certainly disagree about the body of evidence and what it currently says.
The more frustrating aspect of the New Scientist article is that it fails to address a slew of other conditions and cognitive deficits that a lack of sleep has been connected to. For instance, lack of sleep has been associated with cardiovascular problems and mood disorders (such as depression and anxiety):
Importantly, the available data from studies in laboratory animals suggest that sleep restriction may gradually change certain brain systems and neuroendocrine systems in a manner that is similar to what is seen in stress-related disorders such as depression (e.g., reduced serotonin receptor sensitivity and altered regulation of the hypothalamic-pituitary-adrenal axis). Such data support the view that insufficient sleep, by acting on stress systems, may sensitize individuals to stress-related disorders. Indeed, epidemiological studies suggest that sleep complaints and sleep restriction may be important risk factors for a variety of diseases that are often linked to stress, including cardiovascular diseases and mood disorders. (Meerlo et. al., 2008)
There is further evidence that sleep loss is connected to cognitive deficits (Banks & Dinges, 2007), and that sleep loss can lead to increased symptoms of psychopathology in general (e.g., depressive, manic, anxiety and other mental disorder symptoms).