Diagnosing a nocturnal eating disorder in an average-weight man

Background

Nocturnal eating is a common occurrence in the general population and is underdiagnosed. The prevalence of night eating syndrome (NES) has been determined to be equal to or even greater than the classic eating disorders including anorexia nervosa and bulimia nervosa, with a prevalence rate of 1.5%–5.7% in the general population.1 2 In adults with morbid obesity or binge eating disorder, its prevalence can reach 15%.2 In 2008, investigators at the first International Night Eating Symposium in Minnesota categorised night-time eating into two diagnoses, either NES or sleep-related eating disorder (SRED). Familiarity with these relatively new syndromes can prompt clinicians to uncover and treat harmful night-time eating habits that may adversely affect quality of life and cause significant distress to the patient or those living with them.

Case presentation

A man in his 60s presented to the outpatient sleep medicine clinic due to ongoing episodes of night-time eating in the context of interrupted sleep occurring on average seven to eight times per night for the last 11 months. He was accompanied by his spouse who stated that his symptoms made sleeping in the same room impossible. He noted that on waking, he would consciously walk to the kitchen to consume a small amount of food before going back to sleep. When asked whether he did so as a result of hunger, he stated that his primary motive was an urge to return to sleep as quickly as possible and that he thought eating would help. He endorsed full awareness of these episodes. He denied anorexia during the day and eats several meals per day beginning with breakfast.

He has no history of depression, anxiety or restless legs syndrome. He has no other medical history and does not take any medications. He is a non-smoker, does not drink alcohol and does not take any sedative–hypnotic drugs. His work schedule involved travel across time zones and he was on a rotating shift work schedule. He has not noticed his symptoms worsening after travel or shift work. He endorsed snoring, sleep apnoea and daytime fatigue with an Epworth Sleepiness Scale score of 8/24. He has no relevant family history.

Physical exam showed blood pressure of 118/76 mm Hg, pulse rate of 48 beats/min, weight of 202 pounds, and a height of 6 ft 0.5 inch. His body mass index was 27. The rest of the physical exam was normal. He reported being an athlete, and his resting heart rate regularly trends below 60 beats/min.

Investigations

Video monitored polysomnography was done to rule out a primary sleep disorder. It showed evidence of sleep maintenance insomnia and mild obstructive sleep apnoea with an apnoea hypopnoea index of 6.2/hour and a minimum O₂ saturation of 87%. Nocturnal eating episodes were not observed in the sleep laboratory. A night-time eating disorder should not be ruled out based on this finding, given the patient history.

Differential diagnosis

When faced with nocturnal eating, two diagnoses must be on the differential: NES and SRED. The main differences between NES and SRED are personal awareness of night-time eating, subsequent recollection of the episode, and types and amounts of foods ingested. Table 1 summarises these main differences and compares them to our patient. A diagnosis of NES is given to an individual who retains awareness of night-time eating, recalls the episode the following day and ingests a controlled amount of food similar to that eaten during the day. In contrast, a diagnosis of SRED involves an individual with decreased or absent awareness and recollection of nocturnal eating who often ingests an uncontrolled amount of food akin to bingeing and is likely to consume toxic substances or unpalatable foods, such as raw meat or soap.1 3 While both are associated with obesity and mood disorders, SRED is also associated with primary sleep disorders such as sleepwalking, restless leg syndrome and obstructive sleep apnoea.

The diagnosis of NES is based on a set of criteria proposed by Allison et al in 2010.4 Our patient meets all six criteria. For the first criterion, the patient must show a significant increased intake of food during the evening and/or night-time, either through having at least two episodes of nocturnal eating per week or consuming at least 25% of daily food intake after the evening meal. For the second criterion, the patient must be aware and recall these episodes of evening and nocturnal eating. To fulfil the third criterion, a patient must have at least three of the following: (1) lack of desire to eat in the morning, (2) an urge to eat past the last meal of the day, (3) sleep onset or sleep maintenance insomnia, (4) a belief that eating would help overcome the insomnia and (5) a worsening or depressive mood in the evening. Our patient fulfils the third criterion by meeting features 3 with a polysomnography investigation and 2 and 4 through a subjective history. For the last three criteria, the patient must be distressed by these symptoms for a period greater than 3 months, and they cannot be related to any other psychiatric or medical cause. Our patient has been having these symptoms for 11 months, and they have caused great marital tension. They are not associated with substance abuse, an underlying medical or psychiatric condition, or a medication. It is estimated that 64% of individuals diagnosed with NES exhibit the triad of nocturnal hyperphagia, insomnia and morning anorexia with the clear absence of other eating disorders.5

On the other hand, the more established SRED is considered a parasomnia because ‘the eating is often involuntary and poorly recalled, thus resembling sleepwalking’.4 Parasomnias are a group of sleeping disorders characterised by abnormal behaviours while falling asleep, during sleep or while waking up. The first criterion of SRED is simply that a patient must have ‘recurrent episodes of involuntary eating or drinking occurring during the main sleep period’.5 A second criterion indicates that the patient must also experience one of the following: ‘Consumption of peculiar forms or combinations of food or inedible or toxic substances, insomnia related to sleep disruption from repeated episodes of eating with a complaint of nonrestorative sleep, daytime fatigue, or somnolence, sleep-related injury, dangerous behaviors performed while in pursuit of food or while cooking food, morning anorexia, or adverse health consequences from recurrent binge eating of high calorie food’.5 Oftentimes, patients will present with uncomfortable abdominal distension when waking up.3 Of these SRED criteria, our patient only satisfies the aforementioned first criterion but fails to meet the rest of the criteria. If one must assign this individual to either diagnostic category, his symptoms best match with those of the NES.

Treatment

A 50 mg dose of sertraline per night was prescribed. His NES symptoms initially resolved within a week. However, at a 3-month follow-up, he reported recurrence of three to four episodes of nocturnal eating per night. The sertraline dose was increased to 100 mg as a result. In addition to pharmacotherapy, he was advised to limit his sleep to 7–8 hours per night and to start continuous positive airway pressure (CPAP) therapy with a therapeutic apnoea–hypopnoea index due to the obstructive sleep apnoea diagnosed during the polysomnography.

Outcome and follow-up

At the 12-month follow-up visit, he noted complete resolution of his symptoms, including the insomnia, and improvement in daytime alertness. His Epworth Sleepiness Scale score decreased from 8 points to 2 points.