Evidence for genetic influences on sleep disturbance and sleep pattern in twins.

The etiologic role of genotype and environment in sleep pattern (daytime napping, habitual bedtime, and sleep duration) and subjective sleep quality and sleep disturbance was examined using a general population sample of 3,810 adult Australian twin pairs, aged 17-88 years. Genetic differences accounted for at least 33% of the variance in sleep quality and sleep disturbance and 40% of the variance in sleep pattern. There was no evidence for a decline in the importance of genetic predisposition with age. Short-term environmental fluctuations accounted for as much as 30% of the variance, and more stable nonfamilial environmental effects accounted for the remainder. No effect of shared family environment on sleep characteristics was found.