Haemorheological predictors of cognitive decline: the Edinburgh Artery Study

Methods: blood rheology data were collected in 1987/88, and cognitive testing was performed in 1998/99 when the mean (+/- standard deviation) age of the study sample was 73.1 years (+/- 5.0). Follow-up assessment was performed 4 years later. Information was collected on verbal declarative memory, non-verbal reasoning, verbal fluency, information processing speed and a general cognitive factor representing the variance common to the individual test scores. Results: after controlling for age, sex and cognitive performance in 1998/99, blood viscosity (BV) (P < 0.05) and fibrinogen (P < 0.05) predicted decline in non-verbal reasoning over 4 years. When estimated from pre-morbid level, decline in general cognition (P < 0.05), non-verbal reasoning (P < 0.05) and information processing speed (P < 0.01) was associated with BV levels. Haematocrit (HCT) had similar effects (P < 0.01 to P < 0.001). All associations persisted after control for multiple confounders. When examined together, HCT but not BV independently predicted cognitive decline. Conclusions: blood rheology is independently related to cognitive decline in older people. The value of strategies aimed at preserving cognition through influencing blood rheology needs investigation.