Objective: Prior research has established a link between temperament and sleep among children, such that poor sleep (e.g. shorter duration) has been associated with problems in emotion regulation (El Sheikh & Buckhalt, 2005). Specifically, impulsivity has been associated with shorter sleep durations among children (Gruber et al., 2012). Additionally, sleep and temperament in childhood are both heritable. This study examined 1) the heritability of several objective sleep indicators (i.e., duration, efficiency) and temperament and 2) the heritability of the association between objective sleep and impulsivity among twins in middle childhood.
Methods: A subset of 203 families (28.6% MZ, 37.9% same-sex DZ, 33.5% opposite-sex DZ twins) from the Arizona Twin Project (Lemery-Chalfant et al., 2013) were included in this study. Twins (M=8.50, SD=0.52; 49.5% male; 54.1% Caucasian, 26.3% Hispanic) wore an actigraph watch on their non-dominant wrist for seven consecutive days to assess their sleep. Primary caregivers (94.8% mothers) completed questions related to their twins’ temperament. Prior to model fitting in OpenMx, effects for age and sex were regressed out from all variables.
Results: Based on phenotypic correlations impulsivity was the dimension of temperament most strongly related to objective sleep. Specifically, impulsivity was correlated with sleep duration (r = -.21, p < .001) and sleep efficiency (r = -.17, p = .001). Univariate ACE models indicated sleep duration and efficiency were each moderately heritable, with 50% of the variance in duration and 47% of variance in efficiency accounted for by additive genetic factors. Additionally, an ADE model was the best fitting model for impulsivity and indicated a strong additive genetic component (77%). Bivariate model fitting indicated and AE-AE model was the best fitting model between duration and impulsivity (ΔAIC = 2.55, Δdf = 4, p = .24) in which the E21 path was also dropped. This model indicated the shared additive genetic correlation between duration and impulsivity was 0.24. Similarly, an AE-AE (dropping E21) model was also the best fitting model between efficiency and impulsivity (ΔAIC = 1.66, Δdf = 4, p = .17); the additive genetic correlation was 0.23.
Conclusions: Findings suggest the link between sleep and impulsivity is genetic; therefore interventions may need to target sleep and impulsivity among children separately given the unique environmental contributions to each. Future work should 1) consider moderators of the associations between sleep and impulsivity, 2) investigate these associations in other developmental periods, such as adolescence, to determine if additive genetic factors remain a significant influence on sleep and impulsivity associations, and 3) investigate driving factors of the shared genetic associations and potential causal links.
References:
El-Sheikh, M. & Buckhalt, J.A. (2005). Vagal regulation and emotional intensity predict children's sleep problems. Developmental Psychobiology, 46, 3017-317.
Gruber, R., Cassoff, J., Frenette, S., Wiebe, S., & Carrier, J. (2012). Impact of sleep extension and restriction on children's emotional lability and impulsivity. Pediatrics, 130, e1155-1161.
Lemery-Chalfant, K., Clifford, S., McDonald, K., O'Brien, T.C., & Valiente, C. (2013). Arizona Twin Project: A focus on early resilience. Twin Research & Human Genetics, 16, 376-384.
Health (e.g., BMI, Exercise) , Personality, Temperament, Attitudes, Politics and Religion , other , Development
