27 december 2023
A study among 28 elderly people shows that the cerebral blood flow of people who develop early memory complaints decreases faster than that of people without memory complaints. The elderly were examined twice, with an interval of ten years in between, something that is often difficult to implement in scientific research. The results were recently published in The Journal of Cerebral Blood Flow & Metabolism and Geroscience.
The risk of dementia increases as people get older. Ultimately, approximately 20% of people over the age of 80 will develop a form of dementia, such as vascular dementia or Alzheimer’s. No single cause of the disease has yet been found. Much research focuses on how dementia develops and whether it can be prevented.
Brain ultrasounds
One of those studies was conducted by Ralf Weijs, a PhD candidate at Radboud university medical center. He invited a group of elderly people to repeat measurements that they also underwent ten years ago. This made it possible to investigate what changes had occurred in ten years. 28 of the original 48 participants participated again. Their physical and mental condition was assessed using questionnaires and standardized memory tests. They also underwent a cycling test and the blood flow in the cerebral blood vessels was measured using ultrasound.
Weijs: ‘These 28 participants aged from around 70 to 80 years old during the study. We examined a relatively healthy group of elderly people: they were still fit enough to participate in the follow-up study. We did not detect a form of dementia in any of them, but 14 of the 28 elderly indicated that they had developed mild memory problems during those ten years.’
The unique thing about this study is that the researchers examined changes in brain blood flow in the longer term. This is important because these changes are difficult to detect, especially in relatively healthy elderly people. They then linked these changes to the development of early memory complaints. This stage precedes the development of dementia. Weijs continues: ‘Our findings therefore provide better insight into the role of cerebral blood flow in the development and prediction of cognitive disorders. This offers perspective for our search for better prevention and treatment of dementia.’
Poorer blood circulation
The researchers found no significant decrease in cerebral blood flow. However, when they split the group, a significantly stronger decline was found in the participants with developed memory complaints. The blood flow to the brain is important: the better the blood flow to an organ, the better it functions. This is no different for the brain: the better the blood flow, the more oxygen and nutrients reach the brain. This prevents brain cells from dying, causing loss of function.
The researchers also looked at the control mechanisms behind this brain blood flow. They examined the so-called reactivity of the cerebral blood vessels, or how well the vessels respond to changes in the concentration of carbon dioxide (CO2) in the blood. This appeared to deteriorate with age. Another mechanism was autoregulation: this normally ensures that cerebral blood flow remains constant during fluctuations in blood pressure. This autoregulation improved remarkably among the study participants, especially among those who developed memory complaints. Weijs cannot yet give a clear explanation for this, but suspects that there is a compensation strategy.
Kip of no?
The big question now is: is poorer blood flow caused by a brain disease such as dementia, which means there is less ‘demand’ for good blood flow? Or does damage to the vessels and thus poorer cerebral blood flow lead to an increased risk of dementia? It is a chicken-or-egg discussion, says geriatrician Jurgen Claassen of Radboud university medical center. Previous research, conducted by Weijs, showed that people with Alzheimer’s suffer from a sharp decrease in cerebral blood flow, especially in the areas where the disease was most active. That suggests: first brain damage, then a decrease in blood supply. But we also know from other research that a lack of blood flow causes brain damage. So both chicken and egg.
One thing is certain, and that is that lifestyle factors have a major influence on the health of our blood vessels. For example, smoking, high blood pressure and little exercise have a negative effect. Controlled blood pressure keeps the vessels healthy and reduces the risk of dementia by 20 to 30 percent. Weijs: ‘More exercise, for example in the form of sports, is not always easy for the elderly. However, sitting less is usually possible and may yield significant health benefits. Studies show that older people spend a very large part of the day sitting. Especially elderly people with cognitive disorders. That is why we are placing increasing emphasis on research into the importance and effects of a decrease in sitting behavior.’
It is not yet possible to say with certainty whether we can actually prevent dementia with a healthy lifestyle. Although there are indications in this direction, much larger, long-term studies need to confirm this, in which people are followed for ten or fifteen years.
About these publications
This article appeared in The Journal of Cerebral Blood Flow & Metabolism: Cerebrovascular CO2 reactivity and dynamic cerebral autoregulation through the eighth decade of life and their implications for cognitive decline – Ralf Weijs, Madelijn Oudegeest-Sander, Maria Hopman, Dick Thijssen, Jurgen Claassen. DOI: 10.1177/0271678X231219568.
This article appeared in Geroscience: A decade of aging in healthy older adults: longitudinal findings on cerebrovascular and cognitive health – Ralf Weijs, Madelijn Oudegeest-Sander, Janneke Vloet, Maria Hopman, Jurgen Claassen, Dick Thijssen. DOI: 10.1007/s11357-023-00790-w.
2023-12-27 12:02:52
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