SLEEP, Vol. 29, No. 7, 2006
HUNGER AND SLEEP ARE FUNDAMENTAL BIOLOGIC
DRIVES UNDER THE CONTROL OF BOTH HOMEOSTATIC
AND CIRCADIAN INFLUENCES. NOCTURNAL EATING
disorders occur when the coordination of these 2 drives is dys-
regulated, resulting in the disordered eating of a daytime eating
disorder combined with the disordered sleep of a sleep disorder.
Investigations into nocturnal eating have proceeded along 2 par-
allel tracks. Eating disorders specialists use the term night eating
syndrome (NES), coined by Stunkard et al in 1955,1 for patients
with nighttime eating. Criteria for NES include the consumption
of 50% or more of daily calories after the evening meal, eating
after waking from sleep, and morning anorexia.2 Concurrently,
clinical sleep researchers have described sleep-related eating dis-
order (SRED), with a focus on its relationship to parasomnias and
other primary sleep disorders.3,4
Whether NES and SRED are the same or distinct disorders is
unclear. Both involve nearly nightly binging at multiple nocturnal
awakenings, defined as excess calorie intake or loss of control
over consumption. Both have a prevalence of about 1% to 5% of
adults5,6; are predominantly found in women, with a young adult
onset; and have a chronic course.7 Both have a primary morbidity
of weight gain, sleep disruption, and shame over loss of control
over food intake.8,9 Purging, as seen in bulimia nervosa, is rarely
present. Both have familial bases.4,10 Comorbid depression6,11 and
daytime eating disorders4,11 are often observed in both NES and
SRED. Both may respond to similar pharmacologic treatments.2,12
Unfortunately, an assessment of the relationship between NES
and SRED is hampered by the lack of standardized assessments
for nocturnal eating and variations in the diagnostic criteria for
the disorders, as well as a lack of coordinated research between
the 2 specialist fields.
The most prominent cited distinction between NES and SRED
is the level of consciousness during nighttime eating episodes.
Whereas those with NES eat after attaining full awareness, those
with SRED often report that they are “half asleep, half awake”
or even fully asleep during nocturnal episodes and may have im-
paired recollection for the event the following morning.2,4 Some
of the variance between these 2 sets of patients may relate to the
referral patterns and biases of the researchers: sleep disorders
specialists see those with parasomnias and are more concerned
with the fine points of level of consciousness during nocturnal
behaviors, whereas those with an eating disorders background are
more focused on the timing, type, and number of calories con-
To characterize night eating from the 2 specialists’ perspec-
tives in brief: patients with SRED are sleepwalkers who happen
to eat, whereas patients with NES are those with binge eating dis-
order who happen to eat at night. Both of these explanations are
probably too simple. Recent data suggest that the previously ob-
served endocrine abnormalities in NES demonstrating a delay in
the phase relationship of eating to sleep13 are probably the result,
rather than the cause, of night eating.14,15 From the opposite per-
spective, many of the patients with SRED may not have primary
sleep disorders.12 To further confound matters, many of those
with alterations in level of consciousness during nocturnal eating
(and thus diagnosed with SRED) may also have night eating with
full alertness, either at other episodes in the same night or at other
periods during the course of the nocturnal eating disorder.16 In
this way, rather than being two distinct disorders, pure SRED and
NES may reflect opposite ends of a continuum of impairment of
consciousness during nocturnal eating.
Although these diagnostic issues remain unresolved on clinical
and scientific bases, the recent revision of the International Clas-
sification of Sleep Disorders (ICSD) has effectively eliminated
the distinction between the 2 disorders13 (Table 1). The diagnostic
criteria for SRED in the revised ICSD do not specify a level of
consciousness during episodes of nocturnal eating and, thus, in-
corporates NES into SRED. Whether this “lumping” will advance
our understanding of the biology of nocturnal eating disorders is
yet to be seen. However, the new nosology provides a uniform
diagnostic code for all such disorders, facilitating better identifi-
cation across specialty clinics.
The paper by Vetrugno and associates17 from a sleep disorders
clinic in Italy describes 35 patients who in many respects confirm
the previous SRED phenotype: young overweight women with
a chronic course of multiple awakenings from sleep per night
with nocturnal eating. However, only 1 patient had a history of
sleepwalking. Polysomnography demonstrated reduced sleep
efficiency, and two-thirds had a periodic limb movement index
greater than 5. In the laboratory, more than 70% ate at nocturnal
awakenings, all with full consciousness during electroencephalo-
gram-defined wakefulness, consistent with previous reports.4 No
patients had amnesia for the episodes the following morning. In
these latter respects, the patients more closely approximated those
Sleep-Related Eating Disorder and Night Eating Syndrome: Sleep Disorders,
Eating Disorders, or Both?
John W. Winkelman, MD, PhD
Sleep Health Center, Brigham & Women’s Hospital, Newton Center, MA
Dr. Winkelman is a member of the Speakers’ Bureau for Cephalon, King,
Sanofi-Aventis, Sepracor, GlaxoSmithKline, and Takeda; is a member of the
Advisory Board for Pfizer, GlaxoSmithKline, Sepracor, Schwarz-Pharma,
Sanofi-Aventis, Takeda, and Boehringer-Ingelheim; and has received re-
search support from Pfizer, GlaxoSmithKline, UCB Pharma, Boehringer-In-
gelheim, and Schwarz-Pharma.
Address correspondence to: John W. Winkelman, MD PhD, Sleep Health
Center, Brigham & Women’s Hospital, 1400 Center Street, Suite 109, New-
ton Center, Massachusetts 02459; Tel: (617) 527-2227; Fax: (617) 527-2098;
Comment on Vetrugno R; Manconi M; Ferini-Strambi L et al. Nocturnal eating: sleep-related eating disor-
der or night eating syndrome? A videopolysomnographic study. SLEEP 2006;29(7):949-954.
SLEEP, Vol. 29, No. 7, 2006
usually characterized as having NES rather than SRED, even in
sleep laboratory settings.18 Unfortunately, the authors do not spec-
ify whether their patients reported altered levels of consciousness
during their episodes of nocturnal eating outside the sleep labora-
tory. The presence of full alertness during such episodes on poly-
somnography is not a legitimate test of their standard behavior
(as is clear with parasomnias). Thus, it is unclear whether this is
another common example in medicine of “didn’t ask, so don’t
The Vetrugno report includes the first documentation of recur-
rent sleep-related masseter and orbicularis oris electromyographic
activity in SRED, confirmed by video polysomnography to be
masticatory and swallowing behavior. This periodic activity was
present in most (29/35) of the patients at high rates (mean of 116
movements per patient per night), occurred during stages 1 and
2 sleep (and not during wake), and was associated with electro-
encephalogram arousal and tachycardia. Such electromyographic
activity has previously been named rhythmic masticatory-muscle
activity and is seen in bruxism.19 The co-occurrence of periodic
limb movements of sleep and this masticatory behavior suggested
to the authors that SRED and restless legs syndrome/periodic limb
movements of sleep may have a common dopaminergic mecha-
The inclusion of a definition of SRED in the revised ICSD
that consolidates all nocturnal eating disorders presents multiple
opportunities for advancement in this area. With consistently de-
fined patient populations, questions of prevalence, clinical hetero-
geneity, course, familial prevalence, and therapy can be addressed
more definitively. SRED may eventually be split into subtypes
in the future based upon clinical features (e.g., amnesia), poly-
somnographic characteristics, or associated sleep or daytime eat-
ing disorders. Coordination between specialists in sleep disorders
with those researching energy regulation and cognition has already
provided new insights,20,21 which can now hopefully be applied to
patients with night eating. Finally, recognition of SRED by the
revised ICSD may ultimately provide legitimacy to this highly
impairing disorder in an era suspicious of “new” diagnoses.
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a pattern of food intake among certain obese patients. Am J Med
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3. Schenck CH, Hurwitz TD, Bundlie SR, Mahowald MW. Sleep-
related eating disorders: polysomnographic correlates of a hetero-
geneous syndrome distinct from daytime eating disorders. Sleep
4. Winkelman JW. Clinical and polysomnography features of sleep-
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5. Rand CS, MacGregor AM, Stunkard AJ. The night eating syndrome
in the general population and among postoperative obesity surgery
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MG. Nocturnal eating syndrome in adults. Sleep 1994;17:339-44.
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Table 1—Definition and Diagnostic Criteria for Sleep-Related Eating
A. Recurrent episodes of involuntary eating and drinking occur during
the main sleep period.
B. One or more of the following must be present with the recurrent
episodes of involuntary eating and drinking:
1. Consumption of peculiar forms or combinations of food or ined-
ible or toxic substances.
2. Insomnia related to sleep disruption from repeated episodes of
eating, with a complaint non restorative sleep, daytime fatigue,
3. Sleep-related injury.
4. Dangerous behaviors performed while in pursuit of food or
while cooking food
5. Morning anorexia.
6. Adverse health consequences from recurrent binge eating of
high caloric food.
C. The disturbance is not better explained by another sleep disorder,
medical or neurologic disorder, mental disorder, medication use or
substance use disorder (hypoglycemic states, peptic ulcer disease,
reflux esophagitis, Kleine-Levin syndrome, Kluver-Bucy syndrome,
and nighttime extension of daytime Anorexia Nervosa (binge/purge
subtype), bulimia nervosa, and binge eating disorder).
aFrom The International Classification of Sleep Disorders: Diagnostic
and Coding Manual, 2nd ed. Westchester, IL: American Academy of
Sleep Medicine; 2005:174-5.