Dementia Blood Clots

Researchers have postulated that a link exists between brain embolism (a blood clot in the brain) and dementia. Results of a University of Manchester study published in the May 2006 edition of BMJ (formerly the British Medical Journal) support this hypothesis. If supported by additional studies, the University of Manchester blood clot/dementia study may mark a turning point in dementia treatment and prevention techniques.

The Brain Embolism Link to Dementia

While a stroke or a severe blood clot in the brain produces identifiable, obvious symptoms, researchers have considered that less obvious brain embolism activity may account for dementia. So-called “mini-strokes,” or silent cerebral infarctions, may occur without any observable symptoms. Mini-strokes leave residual debris, or cerebral emboli, in the brain.

The connection between dementia and the presence of certain blood clot risk factors further supports the brain embolism-dementia hypothesis. Alzheimer’s disease and vascular dementia account for eighty percent of all dementia cases. Additionally, both are associated with brain embolism risk factors such as high blood pressure, smoking, diabetes and high cholesterol.

Blood Clot Observation in Dementia Cases

Headed by Dr. Charles McCollum, the University of Manchester dementia study included 320 participants and focused on the blood clot rate in Alzheimer’s and vascular dementia cases. Participants were divided into three separate groups:

  • Alzheimer’s patients: 85 participants
  • Vascular Dementia patients: 85 participants
  • control group: 150 participants split into two groups.

The control group was matched with dementia patients according to sex and age. Study participants were monitored for spontaneous blood embolism evidence over an hour, using transcranical Doppler technique (a form of ultrasound).

After only one hour of observation, the results were remarkable. The study detected evidence of previous brain embolism and blood clot activity in 40 percent of the Alzheimer’s patients and 37 percent of the vascular dementia patients. In contrast, the control groups had much lower rates of blood clot evidence: fifteen percent for the Alzheimer’s disease control group and fourteen percent for the vascular dementia control group.

Further Study of the Blood Clot-Dementia Hypothesis

The University of Manchester study suggests that further study of the brain embolism-dementia connection is warranted. Study leaders hypothesized that, had participants been monitored for several hours, the percentage of dementia participants with blood clot evidence would be much higher.

The study also suggests that Alzheimer’s disease and vascular dementia, the two most common types of dementia, have similar causes. Consequently, they may have more in common than was previously thought. Further testing to verify the blood clot-dementia connection could provide new approaches to dementia treatment and prevention.


Medical News Today. (1 May 2006). Blood clots may hold key to treating dementia.

Osterweil, N. (28 April 2006). Blood clots linked to alzheimer’s and vascular dementias.