Amerindian (but not African or European) ancestry is significantly associated with diurnal preference within an admixed Brazilian population

ABSTRACT

Significant questions remain unanswered regarding the genetic versus environmental contributions to racial/ethnic differences in sleep and circadian rhythms. We addressed this question by investigating the association between diurnal preference, using the morningness–eveningness questionnaire (MEQ), and genetic ancestry within the Baependi Heart Study cohort, a highly admixed Brazilian population based in a rural town. Analysis was performed using measures of ancestry, using the Admixture program, and MEQ from 1,453 individuals. We found an association between the degree of Amerindian (but not European of African) ancestry and morningness, equating to 0.16 units for each additional percent of Amerindian ancestry, after adjustment for age, sex, education, and residential zone. To our knowledge, this is the first published report identifying an association between genetic ancestry and MEQ, and above all, the first one based on ancestral contributions within individuals living in the same community. This previously unknown ancestral dimension of diurnal preference suggests a stratification between racial/ethnic groups in an as yet unknown number of genetic polymorphisms.

KEYWORDS:

• Admixture
• American Native Continental Ancestry Group
• Brazil
• chronotype
• circadian rhythm
• diurnal preference
• sleep homeostasis

Acknowledgments

This study was supported by awards from CNPq to HV and MvS (400791/2015-5), and by the Global Innovation Initiative to MvS (jointly funded by the British Council and the UK Department of Business and Skills). The data collection was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP 2012/05447-0; 2012/12042-7; 2013-17368-0), and PROADI_ SUS (25000.180664/2011-35).

Declaration of interest

The authors have no conflicts of interest to declare.