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4 Needing Versus Desiring More Sleep
Sleep Debt: ‘Societal Insomnia’?
question and invites a positive response, as will ‘would you like more
pay’, ‘longer vacations’ and so on? But how many of us are prepared to
forgo time and effort in achieving these ends, including in taking more
We  investigated this apparent desire for more sleep by using more
indirect questioning methods. Almost 11,000 adults completed our simple but more discerning questionnaire that avoided leading questions but
asked: the times usually going to sleep at night and wake up next morning (from which we calculated usual sleep length); how much sleep they
wanted each night (i.e. desired sleep length), their general level of daytime sleepiness, from using the Epworth Sleepiness Scale  (ESS—see
Sect. 9.2), and whether they had a stressful lifestyle. Of particular importance was that we wished to gauge their resolve in obtaining such extra
sleep, and so we then asked, ‘if you had an extra hour in the day, how
would you prefer to spend it?’ Several alternatives were given from which
to choose, these being: playing sport or exercising, socialising, reading or
relaxing, watching TV or a film, listening to radio, working, sleeping or
Women had a greater desire for more sleep than did men, in wanting
an average of 8.0 hours versus 7.37 hours’ sleep as was the case for men.
Nevertheless, when we assessed the differences between actual and these
desired sleep durations, to give an apparent sleep deficit, this averaged
25 minutes for men and 29 minutes for women, which were not large
amounts. However, the other outcomes were more surprising, especially
as we might have expected that the larger this apparent sleep deficit, the
greater would be the daytime sleepiness. But this was not so, as there
was no such relationship for any age group, for neither men nor women.
Moreover, irrespective of the size of this apparent deficit, and with around
50 % of our participants seeming to desire more sleep, at least to some
extent, only 20 % of the latter opted to take the extra sleep option rather
than those alternative waking activities, even those who were more likely
to report moderate or greater levels of daytime sleepiness. It seemed that
wanting more sleep was not necessarily synonymous with actually taking more sleep, but in seeming to want more time to oneself, which was
largely associated with a more ‘stressful lifestyle’. Again, it can be seen
that extra sleep may not be the only anodyne for an apparent sleep deficit.
Inasmuch as we also found that young adults sleep longer than older
adults, with women sleeping longer than men, these findings reflected
similar outcomes from other more general population studies of sleep,
e.g. [3, 4], indicating that our sample population was not unusual. In
general, women, here, were rather more likely to choose that extra hour
for sleeping (23% versus 19% for men), but according to the ESS, women
were no sleepier than men, with similar average ESS scores, which were
also typical of the population at large, as reported by other investigators.
Overall, we found that these apparent sleep deficits did not change with
age, although rather more of the younger groups opted for the extra hour
in sleeping (men: 18 % for younger versus 15 % for older; women: 24 %
versus 19 % for older).
Finally, in a subsequent, much smaller study of ours , 43 healthy
young adults had their sleep monitored for a week, at home, by using
wrist actimeters. We had previously asked them how much sleep they
needed, with the difference between this and the recorded sleep giving an
indication of the extent of any apparent sleep debt. Despite the range in
this debt, it bore no relation with our measures of their daytime sleepiness, as determined by the MSLT and reaction time testing, as well as by
the ESS. We concluded that factors other than sleepiness seem to influence these apparent sleep deficits.
The sleep durations in Figs 2.1 and 2.2 are not detailed enough to reflect
findings that women tend to sleep for around 15 minutes longer than
men, which is more apparent in those younger than 45 years of age,
and has been reported in a variety of studies, including ours , as well
as from UK National Statistics. This is not because of myths relating to
‘more delicate constitutions’, but may well be due to women having more
deep or slow wave sleep (SWS—as identified by ‘delta’ EEG activity—see
Sect. 6.1), and a sign of their having greater brain (i.e. cortical) recovery
during sleep. This in turn indicates that women tend to work their cerebral cortices harder than the age-related man. Women seem to multitask
to a greater extent than men, which requires dealing with information
Sleep Debt: ‘Societal Insomnia’?
from different sources and senses, then selecting which piece of information to attend to and what to ignore, including having quickly to
decide on actions and priorities; all of these are cortically demanding and
create much ‘brainwork’ than, say, reading, completing a crossword, or
undertaking tasks sequentially during the day, or having all one’s attention focused on a computer screen. Coincidentally or otherwise, maybe
owing to a greater degree of ‘use it or lose it’, and that women happen to
retain more SWS with age, the female cortex also ages more slowly than
that of men, by about 5 years. So, by the healthy age of 75, the cognitive
ability of the female brain is comparable with that of a 70 year old man.
More about this ‘brainwork’ in Chaps. 10 and 11.
Although twice as many women as men consult their doctors about
insomnia or other sleep problems, this may be a result of men being
more reluctant to go and seek help. Or maybe the women’s sleep is more
likely to be disturbed by their male partner rather than vice versa? This is
not only because snoring is more frequent in men but, for example, in a
double bed, the movements of the heavier partner will rock and disturb
the other, lighter one, to a greater extent
For Better or For Worse?
There is a widespread belief that in western countries life today is busier,
with greater constraints on sleep time. Although a wide variety of new
findings, described in a comprehensive review  of our daily use of
time over the last 60 years, does not specifically include sleep time, it
seems that work hours have not changed. In contrast, leisure time has
increased somewhat, but there is little support that we are ‘working
harder’, cf. . We tend to overestimate the time we spend working
(including in the USA), and that those who work longer hours tend to
overestimate the most, cf. . However, these conclusions exclude two
demographic groups: single working parents and “well educated professionals, especially those with small children” cf. . Interestingly, the
latter “includes many of the academics who study and discuss the phenomenon” cf. . Of course, nowadays, it is a ‘badge of honour’ to state
that one is busy.
If we did sleep for longer a century or so ago, then why not reverse this
perspective and argue that our ostensibly shorter sleep today is fine for us,
even more ‘natural’? Since in those days if people did sleep for longer they
were probably none the better for it, as so many aspects of life were different, being under conditions that few of us today would wish to revert to.
Finally, merely to judge sleep by quantity, to the exclusion of its quality
presents only a limited perspective on the need for sleep. Besides, from
the few ‘naturalistic’ studies of seasonal changes to sleep, it is apparent
that our sleep duration is somewhat flexible. That is, there is a range of
quite tolerable ‘biological adaptability’ within our sleep, just like there is
in most, if not all, of our other biological functions.
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