By Jim Horne, author of Sleeplessness

Apparently, all too many of us are suffering from chronic sleep loss, commonly known as ‘sleep debt’. This ‘societal insomnia’ is largely attributed to the pressures of modern waking life, and appears to be yet another cause of obesity, cardiovascular disease, even depression. Besides, such claims further add to the worries of those actually suffering with insomnia, striving for even six hours sleep, only to hear that 8 hours or more is the ideal ‘healthy goal’.

Yet, human nature being what it is, little has actually changed since Victorian times, when ‘sleeplessness’ was a common topic of medical debate. Plus ça change as, for example, in 1894 the British Medical Journal lamented that, ‘The hurry and excitement of modern life is held to be responsible for much of the insomnia of which we hear; and most of the articles and letters are full of good advice to live more quietly and of platitudes concerning the harmfulness of rush and worry. The pity of it is that so many people are unable to follow this good advice and are obliged to lead a life of anxiety and high tension.’

Claims that not so long ago we slept for longer, largely stem from misinterpretations of a commonly cited 100 year old study - not on adults, but from teenagers, who indeed slept around 9 hours (and still do today!) However, findings over the last 50 years show our average 7 hour adult sleep to have changed little in the UK. Elsewhere, for example, in Scandinavia, it has fallen only by 20 minutes, and in the USA the proportion of adults sleeping fewer than 6 hours has increased by less than 2%.

Not only are there natural individual differences in sleep duration, but simply judging sleep merely by its length overlooks the importance of its quality, as hour by hour, a night’s sleep is not equivalent in terms its recuperation. As one might expect, sleep at its beginning, reflected by ‘deep sleep’, is more beneficial than sleep towards its end, when REM (dreaming) sleep is more prolific.

Of course, we also sleep for pleasure, beyond its necessity, as in those ‘lie-ins’, which are not necessarily a sign of catching up on sleep debt. Similarly, we can eat and drink in excess of need, simply for enjoyment. Moreover, when people are asked that leading question, ‘would you like more sleep?’, it invites a positive response, but not necessarily a need for more sleep; just perhaps  more time to oneself, as we have found.  

The acid test of insufficient sleep is sleepiness throughout much of the day, with periods of unwanted falling asleep; not just in the early afternoon when many of us have a natural ‘dip’. Assertions that healthy adults can, unknowingly, have chronic sleepiness, are largely based on very sensitive, and arguably oversensitive sleep laboratory tests.

That sleep debt leads to obesity and related disorders is a questionable often cited claim, but largely based on correlations, where both aspects are ‘co-morbid’, being due to a common underlying cause. Thus, more sleep alone will not necessarily alleviate these health issues. Besides, statistically highly significant findings, here, can seem very alarming when based on very large numbers of patients or participants, as such outcomes can still be too small to be of real clinical concern. It can be quite misleading to assume that statistical significance is always the same as clinical significance, all too easily leading to potentially worrying distortions of actual risks.

Although short-term laboratory studies of sleep restriction in healthy adults seem to produce temporary diabetes-like symptoms, this restriction is often too severe, often limiting sleep only to around 4 hours a day, leading to stress and overwhelming sleepiness. Besides, chronic insomnia is unlikely to have these effects or cause obesity. Furthermore, few obese people are short sleepers, and there’s little evidence to show that longer sleep, or sleeping tablets, leads to weight loss here. A better use of such time might well be to spend some of it in daily brisk walking, and maybe contemplate a different diet.

It might seem that chronic insomnia alone leads to poorer mental health, but it is more a disorder of wakefulness intruding into sleep, compounded by a self-perpetuating vicious circle of stress, anxiety and a poorer quality of waking life. The accompanying feelings of being ‘tired all the time’ and difficulties in concentration, are not so much due to sleepiness and a lack of sleep, but a weariness not overcome by striving for more sleep. Effective treatment comes with a more enjoyable wakefulness achieved by cognitive behavioural therapies aimed at creating a better feeling of wellbeing and a more pleasurable bedtime.

My book (Jim Horne - ‘Sleeplessness – assessing sleep need in society today’ - Palgrave Macmilan, 2016) critically examines with supporting evidence, many aspects of sleep debt, with this synopsis just giving a flavour of some of the aspects covered  

Jim Horne is Emeritus Professor of Psychophysiology at Loughborough University, UK and is a sleep neuroscientist who set up and now runs the Loughborough Sleep Research Centre. He is also affiliated to the School of Psychology, at Leicester University’s College of Medicine, Biological Sciences and Psychology, UK, where he works on various cross-disciplinary neuroscience initiatives.