Nonshared Environmental Influences on Sleep Quality: A Study of Monozygotic Twin Differences

Abstract

Research has consistently demonstrated that environmental influences are important for explaining the variability in sleep quality observed in the general population. Although there is substantial evidence assessing associations between sleep quality and a host of environmental variables, it is possible that their effects are mediated by genetic influence. A monozygotic twin differences design was used to assess the specific contribution of nonshared environmental influences on sleep quality, whilst controlling for genetic and shared environmental effects in a sample of 380 monozygotic twins (mean age 19.8 years, SD=1.26, range=18-22 years). Participants completed the Pittsburgh Sleep Quality Index and questionnaires assessing several candidate "environmental" measures. When controlling for genetic and shared environmental effects, within monozygotic twin-pair differences in sleep quality were associated with within monozygotic twin-pair differences in general health for males (β=1.56, p<.001) and relationship satisfaction for females (β=1.01, p<.05). For the remaining environmental measures the results suggest that these seemingly "environmental" influences are actually in part dependent on genetics and/or the shared environment. These findings give insight into how specific environments affect sleep and the possible mechanisms behind these associations.

Gene–environment interplay in the context of romantic relationships

“…Results also supported a GxE interaction, in which genetic influences on the variation in physical health were greatest at both high and low levels of marital quality and lowest at the average level of marital quality (evidence of differential susceptibility, see Panel C of Figure 1). With respect to health behaviors, one study found that the association between marital quality and sleep quality appears to be due to nonshared environmental influences, which may again reflect the influence of one’s partner [44]. …”

Quantitative genetic research on sleep: A review of normal sleep, sleep disturbances and associated emotional, behavioural, and health-related difficulties

“…Our own research using the monozygotic twin differences design has confirmed that associations between several traditionally conceptualised 'environmental' variables are likely to intertwine with genetic factors to influence sleep. (106) More studies of this kind will enable us to understand more about the processes contributing to the associations between the environment and sleep problems.…”

Genetic Research on Sleep, Sleep Disturbances and Associated Difficulties

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