Rait-like Individual Differences in the Human Sleep Lectroencephalogram

bstract—We aimed to examine whether commonly observed ndividual differences in sleep architecture and the sleep elecroencephalogram reflect individual traits, which are amenable o a genetic investigation of human sleep. We studied intrandividual stability and inter-individual variation in sleep and leep electroencephalogram spectra across four baseline reordings of eight healthy young men. A similarity concept ased on Euclidean distances between vectors was applied. isually scored sleep variables served as feature vector comonents, along with electroencephalogram power spectra in on-rapid-eye-movement and rapid-eye-movement sleep. he distributions of similarity coefficients of feature vectors evealed a clear distinction between high within-subject simlarity (i.e. stability), and low between-subject similarity (i.e. ariation). Moreover, a cluster analysis based on electroenephalogram spectra in both non-rapid-eye-movement and apid-eye-movement sleep segregated all four baseline ights of each individual into a distinct cluster. To investigate hether high and low sleep pressure affects the similarity oefficients, normalized non-rapid-eye-movement sleep elecroencephalogram spectra of the first and second half of the ecordings were compared. Because the electroencephaloram changes systematically in the course of the night, withinubject variation no longer differed from between-subject ariation. In conclusion, our data provide evidence for traitike characteristics in the sleep electroencephalogram. Furher studies may help to identify distinct phenotypes to earch for genes underlying functional aspects of undisurbed human sleep. © 2005 Published by Elsevier Ltd on ehalf of IBRO.