Hunger and Sleep Are Fundamental Biologic Drives under the Control of Both Homeostatic and Circadian Influences. Nocturnal Eating

876 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 dysregulated, 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 parallel 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 disorder (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 impaired 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 consumed. To characterize night eating from the 2 specialists’ perspectives in brief: patients with SRED are sleepwalkers who happen to eat, whereas patients with NES are those with binge eating disorder who happen to eat at night. Both of these explanations are probably too simple. Recent data suggest that the previously observed 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 perspective, 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 Classification 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, incorporates 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 identification 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 electroencephalogram-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?