Can high blood pressure cause the neurological damage that causes dementia or Alzheimer’s disease after 50 years? This is the thesis advanced by researchers at Inserm in France and the Department of Epidemiology and Public Health at University College London.
In an article in the European Heart Journal, they suggest that at age 50, high blood pressure but below the diagnostic threshold of hypertension may be associated with an increased risk of developing dementia, even for people with no other cardiovascular pathology.
“Previous research has not been able to directly verify the link between high blood pressure and dementia by examining the timing in sufficient detail. In our article, we were able to examine association at the age of 50, 60 and 70 years, and we found different models of association,” says Dr. Jessica Abell, lead author of the study.
A 45% higher risk of dementia
Entitled Whitehall II, the study followed more than 8,600 people aged 35 to 55 years in 1985, whose blood pressure was measured four times between 1985 and 2003. Among these participants (32.5% women ), 385 developed dementia in the years before 2017 when they were on average 75 years old.
Participants with systolic blood pressure of 130 mmHg or greater at age 50 also had a 45% higher risk of dementia than those with lower systolic blood pressure at the same age. On the other hand, this association was not observed at the age of 60 and 70 years.
Interestingly, this link between high blood pressure and dementia was also observed in people who had no cardiovascular problems during the follow-up period. These participants had an increased risk of 47% compared to people with systolic blood pressure less than 130 mm.
Early detection of dementia
How to explain this link between dementia and high blood pressure? According to the researchers, high blood pressure can cause silent or miniature strokes, whose symptoms are therefore rarely noticeable. This series of accidents, on the other hand, damages the white matter of the brain, which contains numerous nerve fibers, and gradually restricts the flow of blood to the brain. This damage can be the cause of cognitive decline from the age of 50.
According to the researchers, this discovery could allow early detection of brain damage in patients with hypertension when they are still undetectable other than MRI and show no clinical sign of dementia. These patients could then be targeted earlier with dedicated medications to prevent further deterioration of brain function. “The problem is that neurological alterations related to hypertension are usually only diagnosed when cognitive impairment becomes evident, or when traditional magnetic resonance shows obvious signs of brain damage.” In both cases, it is often too late to stop the pathological process, “says Giuseppe Lembo, the coordinator of this study.
“We were able to see that in hypertensive subjects, there was a deterioration of the white matter fibers connecting the areas of the brain typically involved in attention, emotions and memory,” says Lorenzo Carnevale, computer engineer and author of the study. “The aspect to consider is that not all the patients studied showed clinical signs of dementia, and in conventional neuroimaging they showed no evidence of brain injury.” Of course, more studies will be needed, but we believe that the use of tractography will lead to the early identification of people at risk for dementia, enabling timely therapeutic interventions. ”
If developed, this early detection method could also be applied to other forms of cardiovascular disease, say the authors of the study.