Eating and its relationships with subjective alertness and sleep in narcoleptic subjects living without temporal cues.
The sleep and meal patterns of normal subjects appear to be governed by a common timing mechanism. To investigate whether the postulated mechanism may be disordered in narcolepsy, a disorder of sleep timing, we analyzed the sleep, eating, and subjective alertness of six narcoleptic subjects and seven normal controls while they lived in a temporal isolation laboratory. When subjects were free to eat and sleep whenever they chose ("free-running"), the meal patterns and nutrient intakes of the free-running narcoleptic subjects and controls were similar; no evidence of an eating disorder intrinsic to narcolepsy was found. When meals were offered on a 24-h schedule, narcoleptic subjects ate more frequently than did the controls. In two of three narcoleptic subjects whose free-running biological days markedly lengthened, intermeal intervals lengthened proportionately. This was evidence that the timing of sleep (bed-dark) periods and meals was indeed governed by a common mechanism. Meal onsets of narcoleptic subjects were preceded by a 90-min period of decreased napping and, when meals were scheduled, by increased subjective alertness. They were followed by a 150-min period of increased napping and decreased subjective alertness. Postprandial deactivation was not found in controls. The deactivation could not be explained by a post-absorptive effect of food, since the contents of meals that were followed by naps did not differ from those that were not followed by naps. While a preabsorptive effect of meals has not been ruled out, we suggest that postmeal deactivation may be evidence that the mechanism that times sleep periods and meals also modulates the temporal pattern of narcoleptic naps.