title: Exploring causality between TV viewing and weight change in young and middle-aged adults. The Cardiovascular Risk in Young Finns study.
abstract: BACKGROUND
  Television viewing time (TV time) is associated with increased weight and obesity, but it is unclear whether this relation is causal.
  
  
  RESULTS
  We evaluated changes in TV time, waist circumference (waist) and body mass index (BMI) in participants of the population-based Cardiovascular Risk in Young Finns study (761 women, 626 men aged 33-50 years in 2011). Waist and BMI were measured, and TV time was self-reported in 2001, 2007, and 2011. Changes in waist and BMI between 2001 and 2011 were studied a) for the whole group, b) in groups with constantly low (≤ 1 h/d), moderate (1-3 h/d), or high (≥ 3 h/d) TV time, and c) in groups with ≥ 1 hour in-/decrease in daily TV time between 2001 and 2011. BMIs in 1986 were also evaluated. We explored the causal relationship of TV time with waist and BMI by classical temporality criterion and recently introduced causal-discovery algorithms (pairwise causality measures). Both methods supported the hypothesis that TV time is causative to weight gain, and no evidence was found for reverse or bidirectional causality. Constantly low TV time was associated with less pronounced increase in waist and BMI, and waist and BMI increase was lower with decreased TV time (P<0.05). The increase in waist and BMI was at least 2-fold in the high TV time group compared to the low TV time group (P<0.05). Adjustment for age, sex, BMI/waist in 2001, physical activity, energy intake, or smoking did not change the results.
  
  
  CONCLUSIONS
  In young and middle-aged adults, constantly high TV time is temporally antecedent to BMI and waist increase.
authors.affiliation: Paavo Nurmi Centre, Dpts of Physiology & Health and Physical Activity, University of Turku, Turku, Finland.
authors.forename: Harri
authors.initials: H
authors.lastname: Helajärvi
authors.affiliation: Unit of Personality, Work and Health Psychology, University of Helsinki, Helsinki, Finland.
authors.forename: Tom
authors.initials: T
authors.lastname: Rosenström
authors.affiliation: Paavo Nurmi Centre, Dpts of Physiology & Health and Physical Activity, University of Turku, Turku, Finland; Research Centre of Applied and Preventive Cardiovascular Medicine, University of Turku, Turku, Finland.
authors.forename: Katja
authors.initials: K
authors.lastname: Pahkala
authors.affiliation: Department of Clinical Physiology, University of Tampere and Tampere University Hospital, Tampere, Finland.
authors.forename: Mika
authors.initials: M
authors.lastname: Kähönen
authors.affiliation: Department of Clinical Chemistry, Fimlab Laboratories, Tampere University Hospital and School of Medicine, University of Tampere, Tampere, Finland.
authors.forename: Terho
authors.initials: T
authors.lastname: Lehtimäki
authors.affiliation: Paavo Nurmi Centre, Dpts of Physiology & Health and Physical Activity, University of Turku, Turku, Finland.
authors.forename: Olli J
authors.initials: OJ
authors.lastname: Heinonen
authors.affiliation: Research Centre of Applied and Preventive Cardiovascular Medicine, University of Turku, Turku, Finland.
authors.forename: Mervi
authors.initials: M
authors.lastname: Oikonen
authors.affiliation: LIKES Research Center for Sport and Health Sciences, Jyväskylä, Finland.
authors.forename: Tuija
authors.initials: T
authors.lastname: Tammelin
authors.affiliation: Department of Medicine, Turku University Hospital, Turku, Finland.
authors.forename: Jorma S A
authors.initials: JS
authors.lastname: Viikari
authors.affiliation: Research Centre of Applied and Preventive Cardiovascular Medicine, University of Turku, Turku, Finland; Department of Clinical Physiology and Nuclear Medicine, Turku University Hospital, Turku, Finland.
authors.forename: Olli T
authors.initials: OT
authors.lastname: Raitakari
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005387:Finland / Q000453:epidemiology; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D012306:Risk; D057185:Sedentary Behavior; D013223:Statistics as Topic; D013690:Television; D013997:Time Factors; D055105:Waist Circumference