Subjective and Objective Actigraphic Sleep Monitoring and Psychopathology in a Clinical Sample of Patients with Night Eating Syndrome, with and without Binge Eating Behaviors

Night eating syndrome (NES) is a clinical phenomenon combining facets of both sleeping disorders and eating disorders (EDs). NES was first described by Stunkard in 1955 in a sample of obese patients 2. Core characteristics included morning anorexia nervosa (AN), Evening Hyperphagia (25% of daily food eaten after 7 p.m.), insomnia, deteriorating mood (worsening in the evening), and emotional distress 2. Diagnostic criteria for NES have been modified many times over the years, generating almost 20 different sets of criteria to date.

In an attempt to clarify this syndrome's diagnostic criteria, an international NES Working Group comprising sleep and ED experts convened in Minneapolis in 2008 and two years later published their consensual set of criteria 1. These diagnostic criteria were proposed and primarily accepted for inclusion in the American Psychiatric Association (APA) DSM-5 edition 3, under "Other specified feeding and eating disorders."

For the current study, we used all proposed criteria published in 2010 1, which include: significantly increased food intake in the evening (Evening Hyperphagia) and/or at night time (night ingestion) of at least 25% of daily food intake; at least two episodes like this per week; and awareness and recall of evening and nocturnal eating episodes. In addition, the daily pattern is manifested by at least three of the following features: morning anorexia; a strong urge to eat between dinner and sleep onset and/or during the night; insomnia; a belief that one must eat in order to sleep; and depressed or worsening mood in the evening. This syndrome is associated with significant distress, is maintained for at least 3 months, and is not secondary to any other medical or psychiatric disorder. These new criteria currently represent the most updated instrument for diagnosing NES.

Although few significant studies have investigated the prevalence of NES, all reports show that the syndrome is common among individuals who are overweight and/or obese. In the general population, approximately 1.5% of adults are affected by NES 4, 5, but among individuals seeking weight loss treatment, the syndrome is significantly more prevalent (e.g., 8.9% in an obesity clinic) 4, 5. Among patients seeking treatment for EDs, such as bulimia nervosa (BN), binge eating disorders (BED), and AN, the prevalence rates for NES were 9%, 16%, and 0%, respectively 6. In a psychiatric population, the prevalence rate is 12.3% for NES 7.

Only a few studies have examined NES among patients diagnosed with EDs 6, 8, primarily in patients with BED 9, 10 and minimally (mainly case studies) among patients with BN 9, 11, 12, 13, 14, 15, 16, 17, 18. Debate continues in the literature regarding the relations between NES and EDs. NES has been conceptualized as a subtype of obesity, a sleep-related eating disorder (SRED), a variant of other EDs, a separate syndrome among EDs, and a sleeping disorder 8.

One of the common symptoms in EDs, specifically among patients with BED and BN, is BE behavior, which is also a primary symptom of NES. BE behavior is characterized by eating a large amount of food, considered excessive, in a defined period of time. This behavior is accompanied by a sense of lack of control over one’s eating throughout the episode. Such BE episodes are associated with: rapid eating, eating until uncomfortably full, eating large amounts when not hungry, solitary eating because of embarrassment, and feeling disgusted, depressed and guilty. These diagnostic symptoms and associated behaviors overlap across the range of EDs, especially among individuals with BED and BN; however, significant differences exist between the two 3, 19. The main difference is that individuals with BN end their binges using compensatory behaviors such as self-induced vomiting, laxative abuse, diuretics, enemas, or excessive exercise – which are not apparent among individuals with BED. Nevertheless, high psychiatric comorbidity exists among individuals who exhibit BE behavior, including both those with BN and BED 20, 21, as well as among those with a diagnosis of NES 22. Studies indicate that NES and BE behavior commonly occur simultaneously in individuals who have been assessed for BED and NES 5, 23.

Some researchers suggest that although these behaviors may well overlap, NES and BED have different underlying behavioral constructs. Moreover, they propose that BED-only, BED with NES, and NES-only subgroups lie on a continuum of psychopathology, where BED-NES is considered the more extreme psychopathological form and NES-only is considered the less extreme form 5, 23, 24, 25.

In addition, these conditions may be differentiated by the nature of their binge episodes, concerns about weight, and loss of control over eating. During BE episodes, individuals with BED are more likely to consume a higher number of calories than individuals with NES and to report a greater sense of loss of control 11, 26, 27, 28, 29, 30. Individuals with NES report fewer concerns about their body weight or shape than those with BED 24, 31 and fewer instances of compensatory behaviors.

The few prior studies that documented the similarities and differences of individuals with BN versus NES mostly examined patients seeking treatment for sleep disorders at a sleep laboratory 6, 9, 10. Two case studies from the late 1980s provided initial reports on the clinical and psychological characteristics of patients with BN who also suffer from NES 17, 18. Yet, the relations among SRED, NES, and daytime ED, in particular in patients with BN, remain unclear. The question of whether BN together with NES is a new subgroup of EDs and should be called BN with SRED or just BN with NES remains unanswered. NES among patients with BN without SRED has been described only in the last decade by groups of researchers in Israel and Missouri who are experts in eating and sleep disorders 6, 8, 10.

Despite their similarities, NES and BE (which includes BE in BN and BED) also have distinct features. Specifically, as opposed to NES, BE does not include sleep disturbances such as waking up in the middle of the night and having a binge episode 8. Some NES patients indicate full consciousness of their Night Ingestion episodes, while some indicate total amnesia 9, 13, 16, 17, 18,32, 33, 34, 35. Few studies have examined the relations between sleep disorders, BE, and NES 35, 36. Most research examined SRED classified according to the American Academy of Sleep Medicine's International Classification of Sleep Disorders 37.

According to sleep researchers, NES is a sleep-related disorder, in particular among those who wake up to eat during the night or who have Night Ingestion. According to the American Academy of Sleep Medicine, SRED represents a break in the night time, when a patient awakens from sleep to eat prior to the final morning awakening. The Academy suggested that a variety of underlying pathological processes lead to Night Ingestion. However, recent evidence suggests this pattern of eating in order to return to sleep bears a striking similarity to the motor restlessness of restless leg syndrome. Importantly, both Night Ingestion and motor restlessness frequently arise and exist simultaneously, suggesting that many cases of Night Ingestion represent a non-motor manifestation of restless leg syndrome 38. Some cases of Night Ingestion may also represent features similar to sleepwalking, where patients partially arouse from sleep and ambulate to the kitchen to eat 38.

Despite such research demonstrating that this population deserves a unique diagnosis, SRED was excluded from the new NES diagnostic criteria in the DSM-5 because it is considered part of existing sleep disorders and not a separate ED 1. Nevertheless, most studies reported to date were conducted before the new diagnostic criteria of NES 1. To the best of our knowledge, none of the studies conducted thus far have related to both populations of BN and BED patients, with and without NES, in clinical settings – to compare their sleep disturbances using the new diagnostic criteria.

Therefore, the two aims of the current study were to compare (a) the subjective (self-reported) and objective (actigraph) sleep patterns, and (b) the levels of ED-related psychopathology characterizing three groups of patients: NES with and without Binge Eating Behavior (NES-only; NES-BE (including those with BED and BN), and BE-only.