Ms. G, age 39, has a body mass index (BMI) >35 kg/m2 and is pursuing bariatric surgery to treat obesity. She is frustrated with dieting and describes a decade of unconscious nocturnal eating, including peanut butter and uncooked spaghetti.
This behavior began after her divorce 10 years ago. Initially she had partial recall of the nocturnal binges, but now describes full amnesia. Treatment for a depressive episode did not control her nocturnal eating.
Sleep-related eating disorder (SRED) can be associated with disrupted sleep, weight gain, and major chronic morbidity. In SRED—involuntary eating while asleep, with partial or complete amnesia—the normal suppression of eating during the sleep period is disinhibited. The disorder can be idiopathic, associated with medication use, or linked to other sleep disorders such as somnambulism (sleepwalking), restless legs syndrome (RLS), periodic limb movement disorder (PLMD), or obstructive sleep apnea (OSA).
SRED is more common in women than men; it usually begins in the third decade of life but can begin in childhood or middle age. About one-half of SRED patients also have a psychiatric illness, usually a mood disorder. Unremitting SRED may lead to psychopathology, as the onset of sleep-related eating usually precedes the onset of a psychiatric disorder by years.
SRED often is unrecognized, but it can be effectively identified and treated. This article examines how to:
- distinguish SRED from nocturnal eating syndrome (NES) and other disorders
- identify precipitating causes
- select effective pharmacologic therapy.
Sleeping and eating: Closely linked activities
Because hormones that regulate appetite, food intake, and body weight also play a role in sleep regulation, patients with eating disorders often have associated sleep disorders. For example, obesity is related to obstructive sleep apnea (OSA)—weight gain is a risk factor for OSA, and weight loss often is an effective treatment.1 Moreover, patients with anorexia nervosa frequently demonstrate sleep initiation and maintenance insomnia.2
Conversely, epidemiologic studies have demonstrated that sleep duration is inversely correlated with body mass index. In particular, individuals with shorter sleep times are more likely to be overweight.3 The nature of this association is unclear; however, hormones that normally regulate appetite are disrupted in patients with sleep deprivation. For instance, leptin is an appetite suppressant that is normally released from adipocytes during sleep, so sleep deprivation may promote hunger by restricting its secretion.4
Differentiating SRED from NES
Eating and sleeping—and disorders of each—are closely linked (Box).1-4 SRED and night eating syndrome (NES) are 2 principal night eating disorders. SRED is characterized by inappropriately consuming food after falling asleep,5 whereas NES is characterized by hyperphagia after the evening meal, either before bedtime or after fully awakening during the night.6
To meet diagnostic criteria for SRED, patients must experience involuntary nocturnal eating and demonstrate at least 1 other symptom, such as:
- eating peculiar, inedible, or toxic substances
- engaging in dangerous behavior while preparing food (Table 1).
Level of consciousness. In both SRED and NES, patients demonstrate morning anorexia. However, patients with NES report being awake and alert during their nocturnal eating, whereas patients with SRED describe partial or complete amnesia. SRED patients with partial awareness often describe the experience as being involuntary, dream-like, and “out-of-control.” Interestingly, hunger is notably absent during most episodes in which patients have at least partial awareness.
Typically, patients cannot be awakened easily from a sleep-eating episode. In this regard, SRED resembles sleepwalking. Sleepwalking without eating often precedes SRED, but once eating develops it often becomes the predominant or exclusive sleepwalking behavior. This pattern has led many researchers to consider SRED a “sleepwalking variant disorder.”
Eating episodes in SRED are often characterized by binge eating, and many patients describe at least one episode per night.5 They usually eat high-calorie foods. The spectrum of cuisine is broad, ranging from dry cereal to hot meals that require more than 30 minutes to prepare. Patients treated at our sleep center report eating foods that are high in simple carbohydrates, fats, and—to a lesser extent—protein. Peanut butter—a preferred item—can lead to near-choking episodes when patients fall asleep with peanut butter in their mouths and wake up gasping for air. Alcohol consumption is rare.
SRED episodes can be hazardous, with risks of drinking or eating excessively hot liquids or solids, choking on thick foods, or receiving lacerations while using knives to prepare food. Patients may consume foods to which they are allergic or eat inedible or even toxic substances (Table 2).5,7-9
Table 1
Differences between expressive and supportive psychotherapy
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| Source: International classification of sleep disorders: diagnostic and coding manual, 2nd ed. Westchester, IL: American Academy of Sleep Medicine; 2005:174-5. |