EEG sleep patterns in man: a twin study.

All-night EEG sleep recording was performed for 3 consecutive nights in 26 pairs of normal male twins (14 monozygotic and 12 dizygotic) in order to investigate genetic components of sleep. The analysis was based on average values of repeated sleep measures and controlled for the effect of cohabitation. Our results indicate that a significant proportion of variance in stages 2, 4 and delta sleep as well as in REM density is genetically determined in man. Genetic influences on stage 1 and REM are strongly confounded by a synchronizing effect of the cohabitational status.