title: Cognitive function and blood rheology: results from the Caerphilly cohort of older men.
abstract: OBJECTIVE
  Vascular lesions are important contributors to cerebral disease, yet relatively little work has been done on relationships between haematological factors and cognitive function. We have explored these relationships in the Caerphilly cohort of older men.
  
  
  METHODS
  The development of vascular disease and the decline in cognitive function are being studied in a cohort of older men in Caerphilly, South Wales, UK. We have recorded a range of life-style, dietary, lipid, haematological and rheological factors which are, or may be, predictive of vascular disease. We have examined the relationships between these and both incident myocardial infarction and stroke, and identified factors relevant to cognitive function.
  
  
  METHODS
  A community-based study based upon a representative population sample of older men. We collected data for the study from around 90% of the survivors of the original cohort.
  
  
  METHODS
  2154 men who were aged 55-69 years at the time blood was taken for the haematological tests and cognitive function was tested.
  
  
  METHODS
  We present data from the AH4 test of general cognitive performance and from choice reaction time, a test of vigilance.
  
  
  RESULTS
  There is a U-shaped relationship between haematocrit and cognitive function, the best cognitive function scores occurring at a mean haematocrit of 0.46. The relationship is significant for the choice reaction time (P < 0.05). The relationship between haematocrit and the AH4 test score is also curvilinear, but it is not significant. Plasma viscosity showed strong and robust relationships, with significantly better cognitive performance and faster reaction times at lower levels of viscosity (both relationships P < 0.001). Plasma fibrinogen concentration did not show any significant relationships with cognitive function. All these relationships are present, but are much weaker, with rheological tests that had been carried out 5 years before the cognitive testing.
  
  
  CONCLUSIONS
  Blood rheology, as estimated by both haematocrit and plasma viscosity, is a significant determinant of cognitive function in older men. On the other hand, the thrombotic potential of blood, as indicated by fibrinogen level, shows no significant relationships. The relationships with rheology seem to be direct, presumably through blood flow at the time of testing, rather than through underlying long-term disease processes.
authors.affiliation: University of Wales College of Medicine, Cardiff, UK.
authors.forename: P C
authors.initials: PC
authors.lastname: Elwood
authors.forename: J
authors.initials: J
authors.lastname: Pickering
authors.forename: J E
authors.initials: JE
authors.lastname: Gallacher
mesh_terms: D000368:Aged; D000375:Aging / Q000097:blood / Q000523:psychology*; D001809:Blood Viscosity; D003072:Cognition Disorders / Q000097:blood*; D015331:Cohort Studies; D003625:Data Collection; D005340:Fibrinogen / Q000032:analysis; D015577:Geriatric Assessment; D006400:Hematocrit; D018056:Hemorheology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012212:Rheology; D006113:United Kingdom
chemical_list: D005340:Fibrinogen