A quantified analysis of sleep electroencephalography in anorectic adolescents

Previous studies on sleep characteristics in anorexia nervosa have led to controversial results. This may be due to either the heterogeneity of the samples studied or to an intrinsic inadequacy of the scoring criteria. To obtain a more detailed analysis we have investigated sleep characteristics in a group of adolescents affected by anorexia nervosa using spectral analysis techniques.

After a baseline night, the sleep-electroencephalograms of 10 adolescent anorectic girls (age +/- SD = 14 +/- 2 years) and 10 age-matched control subjects were recorded and processed by a fast Fourier transformation routine.

Anorectics showed an increased number of awakenings and wakefulness after sleep onset and a reduction of sleep efficiency and slow-wave sleep. Spectral analysis results revealed a significant reduction in the power spectral values of slow-wave activity (SWA; 0.5-4.5 Hz) band in all NREM-REM cycles of sleep and in the undisturbed and stable stage 4. Moreover the anorectic group was characterized by a concentration of SWA in the first NREM-REM cycle with an abrupt decay in the second part of the night. A positive correlation (r2 = .58, p < .01) between body mass index and the amount of SWA was found.

Sleep of anorectic patients seems to be characterized by a weakness of SWA producing mechanisms. The positive correlation between body mass index and the amount of SWA appears to be consistent with the neurobiological consequences of the malnutrition state.