Many doctors conclude that they should no longer treat high blood pressure in the elderly
Failure to treat high blood pressure in the elderly and people with dementia can lead to more heart attacks and strokes. That is the conclusion of clinical geriatrician Jurgen Claassen. Together with colleagues, he wrote a review article on the mechanism of brain blood flow, which challenges these and other incorrect assumptions.
About 20 percent of the heart’s total output is required for the brain to function and maintain our consciousness. ’20 percent is a relatively large amount of blood for such a small organ,’ says Jurgen Claassen, clinical geriatrician at Radboudumc. He is researching the blood flow in the brain in the elderly. ‘As a result, things quickly go wrong when the blood pressure drops: you are less alert, you fall and eventually lose consciousness.’
While the blood pressure in the body is anything but stable. For example, it drops when you get up, and it can fluctuate under the influence of medication. To accommodate these changes, the brain regulates blood flow with a process called auto-regulation. The aim is to keep brain blood flow as constant as possible. ‘It is a kind of suspension system that absorbs the blows,’ says Claassen. “That way we don’t pass out every time we get up.”
Claassen notices that auto-regulation is neglected in medicine. ‘Most doctors still don’t really understand how auto-regulation works,’ says Claassen. “They know it exists, but they never got beyond that one chapter in the textbook.” He therefore wrote a large review article on the current state of affairs together with colleagues, which was recently published in the journal Physiological Reviews.
There was a great need for such a recent article: the last review article in the field of autoregulation was published in 1959. This gap in knowledge is the cause of persistent misunderstandings in medicine, which Claassen hopes to be able to combat with the article. One of these is the idea that the auto-regulation system becomes less effective with age. ‘The idea has arisen that elderly people need a higher blood pressure in the brain to maintain blood supply and consciousness,’ says Claassen. ‘That sounds harmless, but many doctors have concluded from this that they should no longer treat high blood pressure in the elderly. The result is that for decades elderly people have walked around with dangerously high blood pressure, who were much more likely to die from a heart or cerebral infarction. ‘
Another misconception is the assumption that in dementia the autoregulation in the brain is disrupted, resulting in brain damage. ‘It makes sense: with dementia you already have a damaged brain, and the tissue would be more sensitive to oxygen deficiency,’ says Claassen. ‘In addition, you see a greater risk of blood pressure instability and vascular abnormalities in people with dementia. The idea arose that as a result you have to offer those people a higher blood pressure as compensation. ‘
These dangerous assumptions are based on the fact that it is difficult – not only in people with dementia – to study auto-regulation, says Claassen. ‘This has only been possible since the 1960s with complicated techniques, and only if people stayed down. That gave an incomplete picture and explains that little good research has been done. ‘ Today, researchers have a better picture of the effect of autoregulation on blood pressure in the brain thanks to a combination of different techniques.
‘Many small studies have now been carried out into auto-regulation,’ says Claassen. ‘When we add them together, we count enough test subjects to conclude that no age-related change occurs in auto-regulation.’ The kite does not apply to dementia either. ‘There are serious consequences of keeping the blood pressure in the brain high, especially in these people with dementia, who are already susceptible to vascular disease.’
Evidence in hand
Claassen advocates a different treatment of high blood pressure in the elderly, with more knowledge of auto-regulation in mind. “Even if it is difficult, we must keep trying to measure patients with high blood pressure as old as possible, so that we see in the real world that lowering blood pressure does not lead to reduced brain blood flow.”
The same goes for people with dementia, says Claassen. ‘Again, if you do not treat these people in the event of high blood pressure, you run the risk that things will go exactly in the wrong direction. But there is no evidence for that until we have investigated it. We need to look more closely at the process of auto-regulation with the evidence in hand. ‘
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