title: Distribution and heritability of diurnal preference (chronotype) in a rural Brazilian family-based cohort, the Baependi study.
abstract: Diurnal preference (chronotype) is a useful instrument for studying circadian biology in humans. It harbours trait-like dimensions relating to circadian period and sleep homeostasis, but also has ontogenetic components (morningness increases with age). We used the Morningness-Eveningness questionnaire (MEQ) in the Baependi study, a family-based cohort study based in a small town in Minas Gerais, Brazil. The population is highly admixed and has a cohesive and conservative lifestyle. 825 individuals (497 female) aged 18-89 years (average ± SD = 46.4 ± 16.3) and belonging to 112 different families participated in this study. The average MEQ score was 63.5 ± 11.2 with a significant (P < 0.0001) linear increase with age. Morningness was significantly (P < 0.0001) higher in the rural (70.2 ± 9.8) than in the municipal zone (62.6 ± 11.1), and was also significantly (P = 0.025) higher in male (64.6 ± 10.9) than in female (62.8 ± 11.2) participants. Thus, in spite of universal access to electricity, the Baependi population was strongly shifted towards morningness, particularly in the rural zone. Heritability of MEQ score was 0.48 when adjusted for sex and age, or 0.38 when adjusted for sex, age, and residential zone. The reported MEQ score heritability is more akin to those of previous twin studies than previous family studies.
authors.affiliation: 1] Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK [2] Laboratory of Genetics and Molecular Cardiology, Heart Institute (Incor), University of São Paulo Medical School, São Paulo, SP, Brazil.
authors.forename: Malcolm
authors.initials: M
authors.lastname: von Schantz
authors.affiliation: 1] Laboratory of Genetics and Molecular Cardiology, Heart Institute (Incor), University of São Paulo Medical School, São Paulo, SP, Brazil [2] Department and Institute of Psychiatry (LIM 23), University of São Paulo Medical School, São Paulo, SP, Brazil.
authors.forename: Tamara P
authors.initials: TP
authors.lastname: Taporoski
authors.affiliation: Laboratory of Genetics and Molecular Cardiology, Heart Institute (Incor), University of São Paulo Medical School, São Paulo, SP, Brazil.
authors.forename: Andréa R V R
authors.initials: AR
authors.lastname: Horimoto
authors.affiliation: Laboratory of Genetics and Molecular Cardiology, Heart Institute (Incor), University of São Paulo Medical School, São Paulo, SP, Brazil.
authors.forename: Nubia E
authors.initials: NE
authors.lastname: Duarte
authors.affiliation: Department and Institute of Psychiatry (LIM 23), University of São Paulo Medical School, São Paulo, SP, Brazil.
authors.forename: Homero
authors.initials: H
authors.lastname: Vallada
authors.affiliation: Laboratory of Genetics and Molecular Cardiology, Heart Institute (Incor), University of São Paulo Medical School, São Paulo, SP, Brazil.
authors.forename: José E
authors.initials: JE
authors.lastname: Krieger
authors.affiliation: School of Arts, Science, and Humanities, University of São Paulo, São Paulo, SP, Brazil.
authors.forename: Mario
authors.initials: M
authors.lastname: Pedrazzoli
authors.affiliation: 1] Laboratory of Genetics and Molecular Cardiology, Heart Institute (Incor), University of São Paulo Medical School, São Paulo, SP, Brazil [2] Department and Institute of Psychiatry (LIM 23), University of São Paulo Medical School, São Paulo, SP, Brazil.
authors.forename: André B
authors.initials: AB
authors.lastname: Negrão
authors.affiliation: Laboratory of Genetics and Molecular Cardiology, Heart Institute (Incor), University of São Paulo Medical School, São Paulo, SP, Brazil.
authors.forename: Alexandre C
authors.initials: AC
authors.lastname: Pereira
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001938:Brazil; D002940:Circadian Rhythm / Q000502:physiology*; D015331:Cohort Studies; D003710:Demography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012424:Rural Population; D012737:Sex Factors; D012890:Sleep / Q000502:physiology*; D012892:Sleep Deprivation / Q000175:diagnosis / Q000473:pathology; D011795:Surveys and Questionnaires; D014851:Wakefulness / Q000502:physiology*; D055815:Young Adult