BACKGROUND AND AIMS: Orexins/hypocretins are orexigenic peptides implicated in the regulation of feeding behavior and the sleep/wake cycle. Little is known about the functioning of these peptides in anorexia nervosa (AN). The aims of the current study were to evaluate the extent to which orexin-A might be linked to sleep and treatment outcome in AN.
METHOD: Fasting plasma orexin-A concentrations were measured in 48 females with AN at the start of a day hospital treatment and in 98 normal-eater/healthy-weight controls. The Pittsburgh Sleep Quality Index was administered at the beginning of the treatment as a measure of sleep quality. Other psychopathological variables were evaluated with the Symptom Checklist-Revised (SCL90R) and the Eating Disorder Inventory-2 (EDI). Patients were assessed at the start and end of treatment by means of commonly used diagnostic criteria and clinical questionnaires.
RESULTS: The AN patients presented more sleep disturbances and poorer overall sleep quality than did the healthy controls (p=.026) but there were no global differences between groups in plasma orexin-A concentrations (p=.071). In the AN sample, orexin-A concentrations were associated with greater sleep disturbances (|r|=.30), sleep inefficiency (|r|=.22) and poorer overall sleep (|r|=.22). Structural Equation Modeling (SEM) showed that both elevated orexin-A concentrations and inadequate sleep predicted poorer treatment outcome.
CONCLUSION: Plasma orexin-A concentrations contribute to poor sleep quality in AN, and both of these variables are associated with therapy response.
