title: Retinal vessel calibres and haemostasis in black and white South Africans: the SABPA study.
abstract: OBJECTIVE
  Retinal arteriolar narrowing associates with hypertension development and indicates increased cardiovascular risk. Evidence on whether the retinal vessel calibres are related to the haemostatic system is limited, especially in the black hypertension-prone population with a high stroke incidence. We therefore investigated the relationships between haemostatic markers and retinal vessel calibres.
  
  
  METHODS
  We performed a cross-sectional study involving 170 black (mean age, 58 years; 44% women) and 189 white (mean age, 49 years; 52% women) teachers, and determined ambulatory blood pressure, haemostatic factors (fibrinogen, von Willebrand factor, D-dimer, plasminogen activator inhibitor-1 and clot lysis time) and retinal vessel calibres (central retinal artery and vein equivalent). The black and white groups were stratified by median split of the retinal arteriolar calibre.
  
  
  RESULTS
  Both ethnic groups with a smaller arteriolar calibre had higher SBP and narrower venular calibres. In the black population, the central retinal vein equivalent was positively (β = 0.293; P = 0.024) associated with fibrinogen, whereas in the white population, the central retinal artery equivalent (β = -0.256; P = 0.016) was negatively and central retinal vein equivalent (β = 0.234; P = 0.021) positively associated with von Willebrand factor. Furthermore, clot lysis time was negatively associated with the central retinal artery equivalent (β = -0.390; P = 0.014) in the black group and positively associated with the central retinal vein equivalent (β = 0.275; P = 0.008) in the white group.
  
  
  CONCLUSIONS
  Relationships between markers of haemostasis and the retinal vessel calibres exist, and vary between ethnicities. Haemostatic alterations are linked to early retinal microvascular changes, and future studies should investigate whether it translates into an elevated stroke risk.
authors.affiliation: aHypertension in Africa Research Team (HART) bMRC Research Unit for Hypertension and Cardiovascular Disease cCentre of Excellence for Nutrition (CEN), North-West University, Potchefstroom, South Africa.
authors.forename: Leandi
authors.initials: L
authors.lastname: Lammertyn
authors.forename: Aletta E
authors.initials: AE
authors.lastname: Schutte
authors.forename: Wayne
authors.initials: W
authors.lastname: Smith
authors.forename: Marlien
authors.initials: M
authors.lastname: Pieters
authors.forename: Rudolph
authors.initials: R
authors.lastname: Schutte
mesh_terms: D000328:Adult; D001160:Arterioles / Q000473:pathology*; D044383:Black People; D001794:Blood Pressure; D018660:Blood Pressure Monitoring, Ambulatory; D003430:Cross-Sectional Studies; D005260:Female; D063285:Fibrin Clot Lysis Time; D005338:Fibrin Fibrinogen Degradation Products / Q000378:metabolism; D005340:Fibrinogen / Q000378:metabolism; D006487:Hemostasis / Q000502:physiology*; D006801:Humans; D006973:Hypertension / Q000503:physiopathology; D015994:Incidence; D008875:Middle Aged; D010781:Photography; D017395:Plasminogen Activator Inhibitor 1 / Q000097:blood; D012171:Retinal Vessels / Q000473:pathology*; D013019:South Africa; D014699:Venules / Q000473:pathology*; D044465:White People; D014841:von Willebrand Factor / Q000378:metabolism
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; D017395:Plasminogen Activator Inhibitor 1; C051321:SERPINE1 protein, human; C036309:fibrin fragment D; D014841:von Willebrand Factor; D005340:Fibrinogen