Anorectics and bulimics often complain sleep onset insomnia and disrupted sleep. During awakenings bulimics can have binges. Conversely, eating disorders can be a clinical expression of a concomitantly occurring sleep disorder. Two clinical entities have been recently described: the Night Eating Syndrome (NES) and the Sleep Related Eating Disorders. The main goal of this literature review was to better characterize the relationships between eating disorders and sleep disturbances. No specific EEG sleep pattern emerges in anorectic and bulimic patients. However, all studies include several methodological limitations: a few number of patients, heterogeneous patient groups, various diagnostic criteria. The results of studies evaluating the impact of depression on sleep EEG in eating disorder patients are also subject to controversy. The only study examining the relationship between sleep EEG and morphological alterations in anorectics and normal weight bulimics shows that patients with enlarged cerebrospinal fluid spaces spent more time in slow wave sleep and that the duration of rapid eye movement (REM) sleep was reduced. The ventricular brain ratio was negatively correlated with REM sleep. The Night Eating Syndrome consists in insomnia, binge eating and morning anorexia. Other criteria are proposed to characterize the NES: more than 50% of the daily energy intake is consumed after the last evening meal, awakenings at least once a night, repetition of the provisional criteria for more than 3 months, subjects do not meet criteria for bulimia nervosa or binge eating disorder. Patients have no amnesia nor alteration of alertness, and no other sleep disorder. There is no modification of sleep EEG except sleep maintenance. The prevalence of the NES is 1.5% in the general population. Some neuroendocrine disturbances have been found in the NES. The delimitation with eating disorders is not yet clearly established. If it shares the compulsive features with eating disorders, particularly the "Binge Eating Disorder", and occurs during full awakenings, the night eating syndrome may be recognized as a specific eating disorder. The sleep related eating syndrome is also characterized by compulsive binge eating during awakenings. But in this case, night eating is linked with a reduced consciousness and sleep disorders, mainly somnambulism. Patients never experience hunger, abdominal pain, nausea or hypoglycemia. Night-eating takes place invariant across weekdays, weekend and vacations. Patients consumed high caloric foods and fluids but never alcohol and purging does not occur. Diurnal bulimia is frequently associated with the sleep-related eating disorder. In conclusion, the sleep related eating disorder seems rather be a clinical subtype of sleep disorders whereas the NES could be considered as an eating disorder.
