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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3207_Библиотеки_им_академика_М_И_Перельмана.pdf
48 R. Brown and Y. Umar
Insomnia is characterised by the inability to fall asleep or stay asleep
despite adequate attempts. Patients with insomnia typically experience
trouble initiating sleep, waking during the night or early morning, and
they may be unable to fall asleep after waking up. Affected individuals
often report daytime dysfunction, including an impact on social life and
academic or occupational functioning. In addition, they may experience
irritability, reduced concentration, and reduced productivity at work. For
a diagnosis of acute insomnia (Insomnia Disorder) to be made, the symp-
toms must occur at least three times a week for at least 3-months, whereas
chronic insomnia is diagnosed when the person experiences two or more
episodes of insomnia in a single year [41, 42].
The aetiology of insomnia is reported to be multifactorial [43]. It often
occurs in the context of ill-health and comorbid illness including med-
ical conditions (e.g. chronic pain) [44] and psychological disorders (e.g.
depressed mood) [41], and it can be triggered by stressful life situations
(e.g. work stress) or the person’s response to them [45, 46]. For example,
people with insomnia tend to report higher perceived stress than good
sleepers and they feel less control over the stressful situations in their lives,
which may exacerbate the insomnia [43, 47]. Several theoretical models
have been advanced to explain the manner in which insomnia is likely to
develop and be maintained [43], including the role played by cognitive
and somatic hyper-arousal [48].
OSA is characterised by periods of shallow or difficult breathing that
can interfere with sleep quality [49]; that is, it is a form of sleep-disordered
breathing (SDB) [50]. Clinically, SDB falls on a spectrum from snoring to
sleep disorders, including OSA [50]. OSA can lead to medical complica-
tions, most commonly, cardiovascular conditions, including hypertension
[50]; and it is associated with an increased risk of mortality and reduced
quality of life. High comorbidityalso exists between OSA and several med-
ical disorders (e.g. diabetes mellitus type-II, overweight/obesity), making
it a costly condition to manage in clinical practice [49, 50]. Older age,
obesity, large neck size, and behavioural factors (e.g. alcohol intake) are
known to be risk factors for the development of OSA, as well as a family
history of the disorder [50]. It is a common disorder in patients who are
undergoing bariatric surgery with the majority (71%) of them meeting
criteria for an OSA diagnosis [51].
3 Overweight/Obesity and Concurrent Disorders… 49
RLS is characterised by uncomfortable sensations in the thighs and
calves that can prevent the initiation and/or maintenance of sleep. The
sensations are typically coupled with the perceived need to frequently
move the affected limb(s). Symptoms typically occur when the patient is
trying to relax or rest [52], and they are not reduced until the person moves
their legs (e.g. walking). Although the urge to move the limbs can persist
during the day, it appears to worsen at night [53]. RLS symptoms can
mimic those of other conditions including stress, anxiety, and diabetes;
thus, great care needs to be taken to correctly distinguish it from other
disorders [52]. Little is known about the aetiology of RLS [52], although
the condition is suggested to have a genetic basis [54] and the risk of
developing the condition is known to increase with advancing age and it
is more common in women [38] and people with heart disease [35].
Other rarer sleep disorders have been described in the scientific lit-
erature, including sleepwalking (i.e. somnambulism), which along with
other motor behaviour (e.g. sitting up, fumbling around), typically occurs
during Stages 3–4 NREM sleep, and it can adversely impact upon sleep
quality [55]. However, there is insufficient space here to discuss them in
detail, although, as discussed in Sect. 3.3, night eating syndrome is known
to be characterised by impaired sleep [56], and its incidence is higher in
overweight/obese people than in normal-weight people [57].
In summary, the three most common sleep disorders have a tendency
to co-exist with other medical conditions, including overweight/obesity,
diabetes mellitus type-II, heart disease, and affective distress. For example,
large datasets h ave shown that obesity is highly comorbid with OSA [6]
and insomnia [40], and more weight (and visceral fat) are risk factors for
the development of OSA [58, 59] and insomnia. For instance, in a 10-
year prospective study, insomnia prevalence estimates were shown to be
predicted by obesity and a number of lifestyle factors, including physical
inactivity and alcohol dependence; all of which can increase the risk of
developing insomnia in men [60].
Overweight/obesity (or proxy measures of it; e.g. high BMI) is linked
to specific changes in sleep; for example, obese people tend to report sig-
nificantly shorter sleep duration and greater subjective sleep disturbance
than non-obese people. Additionally, waist circumference is reported
to be inversely correlated with sleep duration; that is, the greater the
50 R. Brown and Y. Umar
waist circumference the shorter the sleep duration [61, 62]. Furthermore,
shorter sleep duration is known to be a risk factor for later obesity [63,
64]. Patel and colleagues [63] found that people who slept less than 5-
hours/night were 3.7 times more likely to be obese than those who slept
7–8 hours/night. However, a review by Patel and Hu [65]showsthat
researchers have reported that a U-shaped relationship exists between
sleep duration and BMI. Nevertheless, it is evident that a bidirectional
relationship exists between impaired sleep and overweight/obesity; that is,
impaired sleep increases the risk of overweight/obesity, and weight disor-
ders also increase the risk of impaired sleep.
A similar relationship has been observed between sleep and weight in
children and adolescents. In the Australian Health and Fitness Survey, sleep
duration was found to be negatively related to BMI and waist circumfer-
ence in boys (but not girls), in a large sample of 7–15 year olds. In particu-
lar, boys who slept 5–8 hours/night were 3.1 times more likely to be over-
weight than those who slept ≥10 hours/night [66]. However, in another
Australian study, shorter sleep duration was related to a greater obesity
risk in both female and male children aged 5–15 years and a stronger
correlation was detected in younger children [67]. Similarly, Chinese 3–4
year olds who slept 9–9.4 hours/night were 4.8 times more likely to be
obese than those who slept >11hours/night [68].
Thus, a significant relationship exists between shorter sleep duration
and greater obesity risk in children and adults, as shown in meta-analyses
[65, 69]. However, many of these results were derived from cross-sectional
studies, although several large longitudinal studies have detected a signifi-
cant relationshipbetween obesityand impairedsleep. Ina 3-year retrospec-
tive longitudinal study of 21,469 adults, people who slept ≤5 hours/night
were morelikely to gain weight and become obese than those who slept ≥7
hours/night, aftercontrolling for age, gender, andclinically relevant factors
(e.g. alcohol intake, exercise frequency, hypertension, dyslipidaemia, dia-
betes, cerebral infarction, myocardial infarction)[70]. However, inanother
study of 35,247 adults, shorter (<5 hours) and longer sleep durations (≥9
hours) were linked to obesity and weight gain in men (but not women)
at one-year follow-up [71].
Taken together, the results suggest that a robust bidirectional relation-
ship exists between shorter sleep duration to weight gain/obesity, and
3 Overweight/Obesity and Concurrent Disorders… 51
weight gain/obesityto disturbed sleep,in adults, children, and adolescents,
although in some cases, obesity may also be linked to longer sleep. How-
ever, the aforementioned longitudinal and cross-sectional study results tell
us nothing about how impaired sleep is linked to overweight/obesity, for
example, the mechanism/s which underpin the comorbidity, and why the
relationship is bidirectional.
Nonetheless, some empirical studies have explored the manner in which
weight disorders and impaired sleep are related to each other. For example,
several studies have examined whether emotional stress may play a role in
shortening the sleep of obese people [62]. However, other explanations
are likely, including the effects of concurrent stress (or affective distress),
disordered eating (e.g. binge-eating), and dysregulation of eating-related
hormones. That is, as detailed in the next section and in Chapter 7,the
mechanisms underpinning the observed relationship between impaired
sleep and overweight/obesity are likely to be multifactorial.Thus,the
mechanisms may be different in different individuals and/or multiple dif-
ferent risk factors and protective factors may exist in the same individual.
3.3 Overweight/Obesity, Disordered Eating,
and Sleep
Overweight/obesity, weight gain, and impaired sleep are linked to several
types of eating behaviour, including late night-eating and binge-eating.
For example, Night-Eating Syndrome (NES) is characterised by evening
hyperphagia (i.e. consuming at least 25% of daily food intake in the
evening), morning anorexia (i.e. markedly reduced appetite in the morn-
ing) [72–75], and altered sleep patterns [72]. As a result, patients with
NES tend to gain more weight (M = 6.2 kg over 6-months) than peo-
ple without NES, and some go on to develop obesity, suggesting that
night-eating behaviour can contribute to weight gain over time [74]. NES
is relatively rare in the general population, but its incidence is higher in
overweight/obese individuals [76, 77]. For example, only 1.5% of healthy
adults met criteria for NES, whereas 27% of obese adults undertaking
gastric restriction surgery to treat obesity met criteria for the disorder, in a
large sample of obese and non-obese adults [57]. However, the screening
52 R. Brown and Y. Umar
questionnaire for NES (i.e. Night-Eating Questionnaire) [78]tendsto
overestimate the incidence of NES; for example, in one study, only 1.5%
of bariatric surgery patients met criteria for NES using a clinical inter-
view, whereas 8.9% of them were diagnosed with NES using the NEQ
[79]. Furthermore, it is unclear exactly how NES and overweight/obesity
are related to each other; that is, some overweight people who consume
high-calorie foods upon waking at night gain weight over time [80, 81].
However, NES can also be diagnosed in normal-weight or underweight
individuals, especially in younger samples [82, 83], indicating that NES
is not always associated with weight gain and overweight/obesity.
Additionally, NES is characterised by specific alterations in sleep,
including less sleep efficiency, longer sleep onset latency, shorter total
sleep time, and longer wake after sleep onset (WASO), relative to healthy
controls [84]. Patients with NES are also reported to undergo sleep archi-
tecture changes (e.g. less Stages2 and3 sleep),shorter total sleep time, more
sleep disturbances, more awakenings, and poorer sleep quality, although
sleep onset and offset did not differ between the women with/without
NES, as assessed by polysomnography over 3 days. In this study, 93%
of the patients with NES ate when they woke up at night, whereas the
controls did wake up at night, but a similar proportion (93%) did not
eat on any of the three nights [85]. Similar results are reported in other
studies showing that NES patients experience more night-time awaken-
ings than healthy controls [73, 86]. Thus, at least in clinical samples, late
night-eating is likely to adversely impact upon sleep quality, sleep onset,
sleep duration, maintenance of sleep, and the development of insomnia
[56, 75], and delayed sleep onset and insomnia form part of the diagnostic
criteria for NES [72].
Night-eating has also been shown to occur in people without a NES
diagnosis, but prevalence estimates for the behaviour vary in part due to
the use of different night-eating definitions. For example, Striegel-Moore
and colleagues [83] examined the prevalence and correlates of night-eating
in adolescents and adults in two nationally representative samples of peo-
ple aged 13 years and older who provided food diary information for
the National Health and Nutrition Examination Survey III or the Con-
tinuing Survey of Food Intakes by Individuals. Prevalence estimates were
obtained using three different definitions of night-eating, ranging from
3 Overweight/Obesity and Concurrent Disorders… 53
9.3–31.3% of the samples. Several factors were correlated with night-
eating including younger age (i.e. most common in 18–30 year olds and
least common in >65 year olds) and weekend eating, but it was unrelated
to high BMI/obesity, gender, ethnicity or season. Similarly, Sevincer and
colleagues [87] showed that 9.5% of 200 college students screened positive
for NES, and high NEQ score was correlated with impulsively and anxi-
ety/depression symptoms, but not gender, nutritional factors or academic
factors. Additionally, Borges and colleagues [88] found that 15.0% of a
university student sample had NEQ scores ≥25, indicative of a possible
NES diagnosis, and high NEQ score was correlated with stress, anxiety,
and depression levels, but not gender, nutritional status, work, and aca-
demic factors.
Thus, the results suggest that late night-eating is commonly practised in
non-clinical populations, with about one-third of people reporting night-
eating behaviourand 10–15% meeting criteria for NES, although thismay
be an overestimate as most of the above studies focused on younger adults.
In addition, night-eating is related to poor sleep quality in community
samples [84, 89], especially the occurrence of nocturnal ingestion (i.e.
waking at night to eat), but not evening hyperphagia or morning anorexia
[90]. As detailed above, this late night-eating behaviour appears to be
consistently linked to the experience of high stress and affective distress,
but perhaps not overweight/obesity or proxy measures of it. However, in
contrast, in a large Danish study (MONICA cohort study)[91], late night-
eating in obese middle-aged women (n = 12) was found to be related
to weight gain over 6-years (average of 5.2 kg), whereas obese middle-
aged women who did not night-eat (n = 84) added only 0.9 kg over the
same time period; but the relationship was not observed in women in
other weight categories (n = 1050) or men, although there was a trend
in the same direction (i.e. night-eating preceded weight gain). Thus, it is
likely that late night-eating can contribute to significant weight gain in
overweight individuals, at least in women, and more so in middle-aged
rather than younger adults, but not necessarily in normal or low weight
individuals.
However, few prospective longitudinal studies have evaluated the rela-
tionship between night-eating and impaired sleep. Aronoff and colleagues
[56] assessed the risk factors for NES in 110obese metabolic clinic patients
54 R. Brown and Y. Umar
over 4 years, showing that 51% of them met criteria for NES, including
a difficulty in initiating and maintaining sleep. NES diagnosis was cor-
related with male gender, high BMI and severe obesity, suggesting that
it tended to be comorbid with overweight/obesity and sleep problems.
Affected individuals were likely to view their eating behaviour as prob-
lematic if they were young, had a history of a psychiatric disorder (e.g.
major depressive disorder or eating disorder), or if they had high BMI;
but not on the basis of the severity of the NES symptoms, including
impaired sleep [81]. Taken together, the results suggest that the existence
of comorbidities, medical (e.g. obesity) and/or psychological (e.g. depres-
sion, eating disorder diagnosis) was most likely to prompt the perception
that the night-eating was problematic to NES patients.
In summary, the aforementioned research findings illustrate the poten-
tial adverse effects of late night-eating on sleep and weight, in clinical (e.g.
NES) and non-clinical samples (e.g. university students). However, it is
less clear whether the late night-eating precedes the occurrence of impaired
sleep and overweight/obesity or if the reverse is (also) true, although it is
suspected that the night-eating habits will tend to develop first [85].
However, few studies have examined whether a functional relationship
exists between sleep and weight problems in NES patients. Several studies
examined circadianrhythm functioning in NES patients to determine if its
dysfunction can explain the NES—sleep relationship [92]. For example,
Goel and colleagues [93] showed that NES patients had a delayed circa-
dian rhythm for total caloric, fat, and carbohydrate intake, a phase-delay
in leptin and insulin secretion, and a phase-delay in melatonin secretion
in women with NES, relative to those without NES, assessed over three
nights. On the basis of the results, NES was attributed to the dysregula-
tion of patients’ peripheral (e.g. stomach) and/or central (e.g. suprachias-
matic nucleus) circadian timing systems. This mechanism, dysregulation
of the circadian rhythm, including a phase-shift in the nocturnal rhythm
of core body temperature (BT), is examined in Sect. 3.4 for its utility
in explaining the relationship between night-eating, impaired sleep, and
overweight/obesity.
SimilartoNES,sleep-related eating disorder (SRED) is characterised by
recurrent episodes of eating after awakening at night [80, 81]. However,
in contrast to NES, the consumption of food in affected individuals is
3 Overweight/Obesity and Concurrent Disorders… 55
believed to be involuntary, that is, patients may only be partly awake and
unaware of their actions[80]. Inparticular, people with SREDtend tocon-
sume high-calorie low-preparation foods (e.g. ice cream, peanut butter);
and potentially, the food preparation that occurs during the awakening
can put them at risk of injury (e.g. hot drink spill) [80, 94]. Similar to
NES, SRED is linked to the development of obesity and significant weight
gain over time [80], especially if the individual is unable to control their
food consumption.
Finally, Binge-Eating Disorder (BED) is known to be linked to weight
gain, obesity, and impaired sleep. BED is characterised by recurrent
episodes of binge-eating that are not followed by compensatory behaviour,
as is the case with bulimia nervosa [42]. The binge-eating episodes tend
to involve eating past the point of feeling full, eating more than is normal,
and experiencing shame after the binge-eating episode. A BED diagno-
sis is given when the symptoms are present at least once/week for ≥3
months. Lifetime prevalence estimates for BED in the US population are
reported to be 3.5% and 2.0%, in women and men, respectively [95].
However, BED is more common in overweight/obese individuals. For
example, 7.5% of obese adults [96] and 1% of obese children and adoles-
cents meet criteria for BED [97]; which is double the prevalence estimate
in the general population. Additionally, a BED diagnosis is associated with
high BMI [95, 98], more severe obesity, and an earlier onset of the obe-
sity [98, 99]. Longitudinally, overweight/obesity increases a person’s risk of
later developing BED [100].Taken together, the results indicate that BED
is more common in overweight/obese individuals especially people with
an earlier onset of obesity or more severe obesity. Furthermore, obesity is
a risk factor for later binge-eating [5] and obese women who binge-eat are
at greater risk of developing anxiety and/or depression [101].
Risk factors for BED include childhood obesity, negative comments
about one’s shape and weight, childhood stressful life events,and a parental
diagnosis of depression, suggesting that overweight/obesity, stress, and
affective distress may together contribute to the development of BED [5].
However, it is also likely that BED contributes to weight gain and over-
weight/obesity over time. Mechanistically, dietary restraint, which is often
practised by overweight/obese people, is thought to contribute to binge-
eating and greater caloric intake in some individuals, which, in turn, may
56 R. Brown and Y. Umar
lead to weight gain [100]. However, other factors have been proposed to
explain the relationship between BED and overweight/obesity, including
the potential impact of binge-eating on sleep [102]. In a population-based
twin study, binge-eating obese women were shown to have more severe
insomnia than non-binge-eating obese women [101]. Similarly, women
with obesity or BED experienced less sleep efficiency and more awaken-
ings at night, relative to non-bingeing normal-weight women, but the
groups did not differ on other sleep parameters, assessed using actigraphy
and self-report questionnaires over 1 week [102].
Thus, similar to night-eating, binge-eating is linked to impaired sleep,
including insufficient sleep, poor sleep quality, daytime sleepiness, and
disrupted sleep, even after controlling for the effects of age, depression,
obesity, and cohabitation status [103]. However, only a fe w cross-sectional
studies have examined binge-eating in regard to sleep so the results require
verification using a longitudinal study design. Nevertheless, it is apparent
that late night-eating [84] and binge-eating [102] likely both impair sleep
in at least in some individuals; in particular, impaired sleep is a hallmark
symptom of NES and one of the diagnostic criteria for this condition [72].
Furthermore, it is noteworthy that binge-eating is typically practised in
the evening and/or at night [104], thus, binge-eating may impair sleep in
a similar manner to that which is occasioned by night-eating, although it
is unclear exactly what the mechanism/s is in either case.
Nevertheless, binge-eating and night-eating are both reported to be
linked to the presence of stress and affective distress [105, 106]. For
example, binge-eating is often preceded by stressful life events, and/or
low mood and binge-eaters tend to report lower mood than in non-binge-
eaters [107]. Similarly, night-eating is related to high stress and affective
distress in college students [106]. In addition, night-eaters are reported to
have higher plasma cortisol levels, but similar levels of ghrelin, subjective
stress, and hunger ratings relative to non-night-eaters, after exposure to a
laboratory stressor (i.e. Cold Pressor Test) [108]. Furthermore, Jääskeläi-
nen and colleagues [109] showed that female adolescent high-stress eaters
were more likely to consume sugar-free soft drinks, chocolate, and sweets
and be obese than non-stressed eaters, whereas male adolescent stress eaters
were more likely to binge-eat.Thus, binge-eating and night-eating are both
3 Overweight/Obesity and Concurrent Disorders… 57
known to be linked to impaired sleep, including insomnia, and a bidirec-
tional relationship has been observed between the disordered eating and
overweight/obesity, weight gain, and stress/affective distress. It is possible
that stress/affective distress may act to disinhibit the disordered eating,
which if practised at night, may tend to interfere with sleep, although it
is unclear by which mechanism/s.
However, further complicating this picture is the fact that night-eating
and binge-eating tend to co-occur with each other, and there is substantial
comorbidity between NES and BED. For example, some people meet cri-
teria for both NES and BED [79], and more generally, the two behaviour
tend to overlap significantly in the same individuals. Importantly, the
clinical overlap between NES and BED, and the statistical overlap (r =
.4) between night-eating and binge-eating behaviour, may tend to con-
found the investigation of linkages between weight, obesity, sleep, and
eating behaviour [89, 104] especially as both disorders (NES and BED)
are more common in obese individuals than in normal-weight individuals.
Furthermore, there is substantialoverlap in the symptoms of each disorder;
for example, BED and NES are both characterised by eating large quan-
tities of food late at night [104], thus, some researchers have questioned
whether the two conditions are really separable clinical entities.
Nevertheless, other researchers assert that the two disorders are clinically
dissociable. For example, obese patients with either BED or NES who
underwent biliopancreatic diversion surgery were shown to have different
clinical trajectories. Patients with BED were reported to stop binge-eating
after the surgery and they no longer binge-ate 3 years later, whereas the
NES patients continued to night-eat 3-years after the surgery [104]. Thus,
it is likely that the two disorders are independent clinical entities, which
tend to often co-occur [110, 111], although due to the propensity of
each behaviour to occur at night, it is likely that the same (or similar)
mechanisms underpin their putative effects on sleep.
Finally, as detailed in Sects. 3.1–3.3 and Chapter 7, at least some of
the risk factors for impaired sleep, insomnia and overweight/obesity are
similar, including each of the disorders themselves as well as disordered
eating, affective distress, and physical inactivity. This pattern of overlap-
ping risk factors for each of the different-but-related conditions is repeated
throughout this book. That is to say, the disorders, symptoms, and states