title: Sedentary screen time and left ventricular structure and function: the CARDIA study.
abstract: BACKGROUND
  Sedentary screen time (watching TV or using a computer) predicts cardiovascular outcomes independently from moderate and vigorous physical activity and could affect left ventricular structure and function through the adverse consequences of sedentary behavior.
  
  
  OBJECTIVE
  This study aimed to determine whether sedentary screen time is associated with measures of left ventricular structure and function.
  
  
  METHODS
  The Coronary Artery Risk Development in Young Adults Study measured screen time by questionnaire and left ventricular structure and function by echocardiography in 2854 black and white participants, age 43-55 yr, in 2010-2011. Generalized linear models evaluated cross-sectional trends for echocardiography measures across higher categories of screen time and adjusting for demographics, smoking, alcohol, and physical activity. Further models adjusted for potential intermediate factors (blood pressure, antihypertensive medication use, diabetes, and body mass index).
  
  
  RESULTS
  The relationship between screen time and left ventricular mass (LVM) differed in blacks versus whites. Among whites, higher screen time was associated with larger LVM (P < 0.001), after adjustment for height, demographics, and lifestyle variables. Associations between screen time and LVM persisted when adjusting for blood pressure, antihypertensive medication use, and diabetes (P = 0.008) but not with additional adjustment for body mass index (P = 0.503). Similar relationships were observed for screen time with LVM indexed to height, relative wall thickness, and mass-to-volume ratio. Screen time was not associated with left ventricular structure among blacks or left ventricular function in either race group.
  
  
  CONCLUSIONS
  Sedentary screen time is associated with greater LVM in white adults, and this relationship was largely explained by higher overall adiposity. The lack of association in blacks supports a potential qualitative difference in the cardiovascular consequences of sedentary screen-based behavior.
authors.affiliation: 1University of Pittsburgh, Pittsburgh, PA; 2National Heart, Lung, and Blood Institute, Bethesda, MD; 3Northwestern University Feinberg School of Medicine, Chicago, IL; 4Kaiser Permanente Division of Research, Oakland, CA; 5Johns Hopkins Institutes of Medicine, Baltimore, MD; and 6University of Alabama at Birmingham, Birmingham, AL.
authors.forename: Bethany Barone
authors.initials: BB
authors.lastname: Gibbs
authors.forename: Jared P
authors.initials: JP
authors.lastname: Reis
authors.forename: Erik B
authors.initials: EB
authors.lastname: Schelbert
authors.forename: Lynette L
authors.initials: LL
authors.lastname: Craft
authors.forename: Steve
authors.initials: S
authors.lastname: Sidney
authors.forename: Joao
authors.initials: J
authors.lastname: Lima
authors.forename: Cora E
authors.initials: CE
authors.lastname: Lewis
mesh_terms: D000328:Adult; D001741:Black or African American; D001794:Blood Pressure; D001827:Body Height; D015992:Body Mass Index; D003201:Computers; D003920:Diabetes Mellitus / Q000503:physiopathology; D004452:Echocardiography; D015444:Exercise; D005260:Female; D006352:Heart Ventricles / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D006801:Humans; D006973:Hypertension / Q000188:drug therapy; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D057185:Sedentary Behavior; D011795:Surveys and Questionnaires; D013690:Television; D013997:Time Factors; D016277:Ventricular Function, Left; D044465:White People