Is circadian type associated with sleep duration in twins?
We used the community-based University of Washington Twin Registry to investigate the genetic association between circadian type and sleep duration. Habitual sleep duration was obtained by self-report and circadian type was measured using a reduced 5-item Horne–Östberg Morningness–Eveningness questionnaire. Univariate and bivariate genetic analyses were fit using structural equation models. We used multinomial logistic regression […]