How does high blood pressure promote dementia?

Arterial hypertension is a very common disease: almost 1 in 3 adults are affected in France. It is a chronic disease that predisposes affected patients to other types of pathologies, cardiovascular or neurodegenerative. Although their links with the onset of dementia have already been established, the effects of high blood pressure on the brain are unknown. What is the role of blood pressure on cognitive functions? What regions of the brain are affected by high blood pressure?

High blood pressure is a risk factor for cardiovascular diseases and neurodegenerative diseases. How can pressure in the arteries damage the brain and cause dementia? A team looked into the subject and their results have been published in the journal European Heart Journal.

A link between blood pressure and cognitive performance

Numerous data from several banks were used: blood pressure measurements, magnetic resonance imaging of the brain, genetic data, etc. The objective was to study the link between brain structures, blood pressure and cognitive functions. Mendelian randomization was chosen as the statistical method. The authors succeeded in demonstrating that it was high blood pressure that was at the origin of the changes in the patients’ brains thanks to data from a British biobank.

To assess cognitive performance, the fluid intelligence score was chosen. It determines a person’s ability to reason and adapt to new situations. The results obtained were verified on other datasets, in particular an Italian biobank. The results obtained therefore seem to be generalizable to other populations.

Which regions of the brain are affected?

Hypertension is actually defined by two measures. That of systolic pressure when the heart contracts to empty and that of diastolic pressure when the heart relaxes to fill. It was systolic pressure that was directly associated with dementia risk rather than diastolic pressure. Systolic pressure has also been observed to be related to brain structural defects seen in imaging. The regions of the brain impacted were thus able to be identified: the putamen and the white matter.

The putamen is present in duplicate, one in the left brain and one in the right brain. It is involved in the regulation of movements and learning. It uses several neurotransmitters (Gaba, acetylcholine, enkephalin). It is deficient in Parkinson’s disease for example.

White matter is located in the heart of the brain, below the gray matter. It is essentially made up of neurons and allows the propagation of messages in the nervous system. Systolic blood pressure, when elevated, directly affects white matter and deteriorates connections with other parts of the brain, triggering dementias.

A better understanding of the link between blood pressure and cognitive decline will help guide research on possible therapies to be implemented.

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