title: Age, blood pressure, and retinal vessel diameter: separate effects and interaction of blood pressure and age.
abstract: OBJECTIVE
  The association of age and blood pressure (BP) with retinal vessel change is widely reported, with inverse relationships between retinal arteriolar and venular diameter and increasing age and elevated BP. No previous studies have dissected the separate effects of age and BP on the diameter of retinal vessels.
  
  
  METHODS
  This was a population-based, cross-sectional study comprising 3654 participants (82.4% response) aged 49+ years from the Blue Mountains region of Australia. Retinal arteriolar and venular diameters were measured from digital retinal images, using a standardized method, and were summarized as central retinal arteriolar (CRAE) and central retinal venular (CRVE) equivalents.
  
  
  RESULTS
  After adjustment for venular diameter, regression plots, and regression coefficients from linear models demonstrated an inverse relationship between arteriolar diameters and mean arterial BP (MABP) in all age groups-greatest in the <60 age group and progressively diminishing thereafter. Increasing age was associated with greater arteriolar narrowing (of lesser magnitude), in each MABP category (<100, 100-109, 109-129, and >120 mm Hg) with the greatest effect in persons with MABP <100. There was evidence of interaction between age and blood pressure in their effects on arteriolar diameter (P = 0.003). After adjustment for arteriolar diameter, age was inversely associated with venular diameter (the effect was progressively greater for persons with progressively higher MABP), and MABP was positively associated with venular diameter in subjects aged <80 years (interaction P = 0.05).
  
  
  CONCLUSIONS
  These findings demonstrate the importance of elevated blood pressure in arteriolar narrowing, especially in those younger than 60 years and show that venules tend to widen rather than narrow with increasing blood pressure levels.
authors.affiliation: Department of Ophthalmology, the University of Sydney, Center for Vision Research, Westmead Millennium Institute, Westmead, Australia.
authors.forename: Shweta
authors.initials: S
authors.lastname: Kaushik
authors.forename: Annette
authors.initials: A
authors.lastname: Kifley
authors.forename: Paul
authors.initials: P
authors.lastname: Mitchell
authors.forename: Jie Jin
authors.initials: JJ
authors.lastname: Wang
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001160:Arterioles / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D003430:Cross-Sectional Studies; D006801:Humans; D008875:Middle Aged; D012171:Retinal Vessels / Q000502:physiology*; D014699:Venules / Q000502:physiology