Night eating syndrome (NES) appears to be related to disturbed circadian rhythms of food intake., new research suggests. The disorder may also run in families and appears to respond to sertraline treatment.

According to Albert Stunkard, MD, emeritus director of the Weight and Eating Disorders Program at the University of Pennsylvania School of Medicine in Philadelphia, NES is prevalent in about 6% of people who seek treatment for obesity.

First described by Dr. Stunkard in 1955 in the American Journal of Medicine, NES may be stress related and is often accompanied by depression. Individuals with the disorder consume one third or more of their daily calories after their evening meal, sometimes rising from their beds once or twice a night to snack. A 15-item questionnaire is used to diagnose the disorder.

Speaking at the North American Association for the Study of Obesity (NAASO) annual meeting this week, Dr. Stunkard presented some of his group's latest findings.

In their study, the researchers monitored sleep/wake activity over one week in 40 adults with NES and a mean body mass index (BMI) of 35 or higher. Subjects were compared with 45 controls matched for BMI. The researchers also studied 15 individuals with NES and 15 overweight control subjects who spent three days and two nights in a sleep laboratory.

The study resulted in three new findings. The first was that NES involves a disturbed circadian rhythm of food intake while circadian sleep rhythm remains normal.

"The circadian rhythm of food intake is extremely disturbed and the timing is delayed by four or five hours compared to that of in normal people," Dr. Stunkard told Medscape in a phone interview.

According to the researchers, NES "is the first clinical disorder to manifest different circadian rhythms of two biological systems."

Another finding was that 36% of the NES subjects had at least one first-degree relative with the disorder compared with 22% of the control subjects (P = .01).

The researchers also report that NES may be responsive to treatment with the selective serotonin reuptake inhibitor sertraline. In an open-label trial of 17 subjects with NES, 29% of subjects taking sertraline experienced total remission of the disorder, and another 18% improved significantly.

"On average, nighttime awakenings fell by 60%, nighttime ingestions by 70%, and number of kilocalories consumed after supper by 40%," they report.

An article describing these research findings will be published in the January issue of the International Journal of Eating Disorders.

Dr. Stunkard notes that their ongoing research involves studies of the circadian patterns of eight different hormones, including glucose, insulin, adrenocorticotropic hormone, cortisol, leptin, and grehlin.

This study was funded by the National Institutes of Health and Pfizer Pharmaceuticals, the manufacturer of sertraline.