title: The cross-sectional association of sitting time with carotid artery stiffness in young adults.
abstract: OBJECTIVE
  Physical activity is negatively associated with arterial stiffness. However, the relationship between sedentary behaviour and arterial stiffness is poorly understood. In this study, we aimed to investigate the association of sedentary behaviour with arterial stiffness among young adults.
  
  
  METHODS
  Cross-sectional.
  
  
  METHODS
  34 study clinics across Australia during 2004-2006.
  
  
  METHODS
  2328 participants (49.4% male) aged 26-36 years who were followed up from a nationally representative sample of Australian schoolchildren in 1985.
  
  
  METHODS
  Arterial stiffness was measured by carotid ultrasound. Sitting time per weekday and weekend day, and physical activity were self-reported by questionnaire. Cardiorespiratory fitness was estimated as physical work capacity at a heart rate of 170 bpm. Anthropometry, blood pressure, resting heart rate and blood biochemistry were measured. Potential confounders, including strength training, education, smoking, diet, alcohol consumption and parity, were self-reported. Rank correlation was used for analysis.
  
  
  RESULTS
  Sitting time per weekend day, but not per weekday, was correlated with arterial stiffness (males r=0.11 p<0.01, females r=0.08, p<0.05) and cardiorespiratory fitness (males r = -0.14, females r = -0.08, p<0.05), and also with fatness and resting heart rate. One additional hour of sitting per weekend day was associated with 5.6% (males p=0.046) and 8.6% (females p=0.05) higher risk of having metabolic syndrome. These associations were independent of physical activity and other potential confounders. The association of sitting time per weekend day with arterial stiffness was not mediated by resting heart rate, fatness or metabolic syndrome.
  
  
  CONCLUSIONS
  Our study demonstrates a positive association of sitting time with arterial stiffness. The greater role of sitting time per weekend day in prediction of arterial stiffness and cardiometabolic risk than that of sitting time per weekday may be due to better reflection of discretionary sitting behaviour.
authors.affiliation: Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia.
authors.forename: Quan L
authors.initials: QL
authors.lastname: Huynh
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Blizzard
authors.forename: James E
authors.initials: JE
authors.lastname: Sharman
authors.forename: Costan G
authors.initials: CG
authors.lastname: Magnussen
authors.forename: Terence
authors.initials: T
authors.lastname: Dwyer
authors.forename: Alison J
authors.initials: AJ
authors.lastname: Venn
mesh_terms: D000273:Adipose Tissue; D000328:Adult; D001315:Australia; D001794:Blood Pressure; D002339:Carotid Arteries / Q000000981:diagnostic imaging / Q000502:physiology*; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D006304:Health Status; D006339:Heart Rate; D006801:Humans; D008297:Male; D024821:Metabolic Syndrome / Q000209:etiology; D009043:Motor Activity; D010809:Physical Fitness; D011187:Posture / Q000502:physiology*; D057185:Sedentary Behavior; D057566:Self Report; D012737:Sex Factors; D014463:Ultrasonography; D059289:Vascular Stiffness; D055815:Young Adult
keywords: EPIDEMIOLOGY; PREVENTIVE MEDICINE