The moderating role of early-life parental adverse and positive factors in the genetic and environmental contributions to objectively assessed sleep duration in middle childhood.

• Objectively-assessed sleep duration is highly heritable in middle childhood. • Positive parent personality moderated heritability of child sleep duration. • Parental stress and strain moderated heritability of sleep duration in childhood. • Genetic expression of sleep duration may be altered by early-life parental factors. • Parental factors may be central to child sleep health. Early-life positive and adverse parental factors, such as positive parent personality and parental stress, affect the environmental context in which children develop and may influence individual differences in children's sleep health. This study examined the moderating role of early-life parental factors in the heritability (i.e., the extent to which individual differences are due to genetic influences) of objectively assessed childhood sleep duration. A total of 351 families from the Arizona Twin Project were studied. Primary caregivers (95% mothers) reported on multiple dimensions of stress and facets of their own personality when the twins were 12 months old. Seven years later (M age = 8.43 years, SD = 0.68), families completed a home visit, and twins (51% female; 57% White, 29% Hispanic; 30% monozygotic, 39% same-sex dizygotic, 31% other-sex dizygotic) wore actigraph watches to assess their sleep, with caregivers completing similar assessments on their personality attributes and stress. Early-life positive parent personality moderated the heritability of sleep duration (Δ−2LL [−2 log likelihood] = 2.54, Δ df = 2, p =.28), such that as positive parent personality increased, the heritability of duration decreased. Early-life parental stress also moderated the genetic contribution to sleep duration (Δ−2LL = 2.02, Δ df = 2, p =.36), such that as stress increased, the heritability of duration increased. Concurrent positive parent personality and parental stress composites showed similar patterns of findings. Results highlight the likely contribution of parent positive traits and adverse experiences to the etiology of children's sleep health, with genetic influences on children's sleep more prominent in "riskier" environments. Understanding how genetics and environments work together to influence the etiology of sleep may inform prevention programs. [ABSTRACT FROM AUTHOR]