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Cognitive function and blood rheology: results from the Caerphilly cohort of older men
P C Elwood1, J Pickering, J E Gallacher
1University of Wales College of Medicine, Cardiff, UK.
Insights
Blood viscosity and haematocrit levels significantly impact cognitive function in older men. Lower plasma viscosity and a specific haematocrit level correlate with better cognitive performance and reaction times, suggesting direct effects on blood flow.
Area of Science:
- Gerontology
- Neuroscience
- Hematology
Background:
- Vascular lesions contribute to cerebral disease, but links between blood factors and cognition are understudied.
- Cognitive decline is a significant concern in aging populations.
Purpose of the Study:
- To investigate the relationship between hematological factors and cognitive function in older men.
- To identify specific blood properties influencing cognitive performance.
Main Methods:
- A community-based study of 2154 men aged 55-69 years.
- Assessed general cognitive performance (AH4 test) and vigilance (choice reaction time).
- Measured hematological and rheological factors, including hematocrit, plasma viscosity, and fibrinogen.
Main Results:
- A U-shaped relationship was observed between hematocrit and cognitive function, with optimal performance at a mean hematocrit of 0.46.
- Lower plasma viscosity strongly correlated with significantly better cognitive performance and faster reaction times (P < 0.001).
- Fibrinogen levels showed no significant association with cognitive function.
Conclusions:
- Blood rheology, specifically plasma viscosity and hematocrit, significantly influences cognitive function in older men.
- These rheological effects appear to be direct, likely mediated by blood flow, rather than long-term disease processes.
- Fibrinogen levels, indicating thrombotic potential, were not linked to cognitive function in this cohort.
Objectives:
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.
Design:
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.
Setting:
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.
Subjects:
2154 men who were aged 55-69 years at the time blood was taken for the haematological tests and cognitive function was tested.
Main Outcome Measures:
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.