- High blood pressure damages the vessels carrying blood to and around the brain; low blood pressure starves the brain of fresh blood and oxygen
- Studies have linked both conditions to a higher risk of dementia. The good news is that adopting a healthy lifestyle will help regulate your blood pressure
As my doctor approaches me with his blood pressure monitor, I tell him that I suffer with white-coat syndrome – or rather, white-coat hypertension: my anxiety levels and blood pressure rise as soon as I walk into his clinic.
Sure enough, cuff tight about my arm, my heart pounding, the machine beeping, it gives a reading higher than it should be: 140/90, diagnosed as hypertensive Stage 2.
“I promise you, it’s not normally that high!” I bleat.
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My doctor is sceptical and insists on a 24-hour continuous reading. I go home strapped to a mini mobile unit to keep an eye on the numbers overnight: systolic and diastolic.
Systolic (the first number) – indicates how much pressure your blood is exerting against your artery walls when your heart beats.
Diastolic (the second number) – tells you how much pressure your blood is applying to artery walls while the heart is resting in between beats. You want to be aiming for the optimal reading – around 120/80.
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To my relief, as always happens, my blood pressure drops to a healthy level – 125/78 – as soon as I’m within the safe environs of my own space, feet up, in front of the TV, a medicinal glass of red wine to hand.
There are a dozen reasons you should be concerned about your blood pressure, because of its implications for your risk of things such as stroke, heart attack, even kidney failure. A recent study suggests it could be linked with dementia, too.
After the George Institute’s Global Brain Health Initiative in Australia canvassed nearly 30,000 people, it concluded that lowering blood pressure could prevent dementia. A number of earlier studies have suggested the same, but not many followed subjects long enough to really dig deep into the dementia outcomes.
I ask Dr Ruth Peters, an associate professor at the University of New South Wales and lead author of the study, why uncontrolled high blood pressure increases the risk of cognitive decline later on in life – and why we should keep an eye on our blood pressure to protect our brains.
We know that blood pressure tends to rise as we age, Peters says, and we know that having higher blood pressure, even in early midlife – our 40s – can increase our risk of dementia.
A 2021 study published by the American Heart Association found that people diagnosed with hypertension as early as their mid-30s were 61 per cent more likely to present with smaller brains and develop some type of dementia within the following decade than those with normal blood pressure. Few of us have even begun to think about losing our grey matter in our 30s.
High blood pressure can increase our risk of developing dementia in a number of ways, Peters says.
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Probably the most well-known is a stroke. More than half of all stroke deaths are attributed to high systolic blood pressure, and having a stroke increases our risk of developing dementia, usually vascular dementia.
Problems with reasoning, planning, judgment, memory and other thought processes result from damage caused by impaired blood flow to the brain.
Having high blood pressure can also damage blood vessels, including the small blood vessels in the brain, Peters adds.
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My mother had a stroke seven years ago. Is that what contributed to her dementia? Doctors don’t know. They are unsure what caused her stroke – she had no heart arrhythmia, no cholesterol issues, and her blood pressure was low.
Often it was too low, so low she often felt dizzy – even as a child – and in recovery after her stroke, the nurses struggled to raise it. She needed help walking when she got up from lying down; unassisted, she was at risk of crashing to the floor.
We resorted to a diet with a lot of salty snacks and caffeine-laden drinks to try to elevate it. Could that have been to blame? Possibly.
Some studies suggest that low blood pressure – medically referred to as hypotension and diagnosed when those numbers are below 90/60 – is associated with cognitive decline in later life.
It may compromise a healthy, sustained blood flow to the brain because, when your blood pressure is too low, the brain is the first thing to be starved of fresh blood and oxygen – hence the dizziness.
Those with low blood pressure experience a drop in pressure when they sit up or stand from a prone position – hence my mother’s collapsing every time she got up. This was exacerbated because she has never been keen to stay hydrated.
Dehydration is a key cause of low blood pressure; when the body is low on water, blood volume drops, which can cause blood pressure to drop, too.
If blood pressure – high or low – is a significant risk factor for dementia, how does it compare to other risk factors?
Peters says controlling high blood pressure is important for multiple reasons.
It’s never too late, or too early, to start thinking about brain health and adopting a healthy lifestyle to promote it, Peters says. A healthy diet and regular physical activity will help keep your blood pressure at or around the optimal level.
My doctor, still sceptical that I have white-coat syndrome, put me on a low-dose daily antihypertensive. If you’ve been put on meds to control blood pressure, says Peters, make sure you take them as directed.
This is the fourth instalment in a series on dementia, including the research into its causes and treatment, and the quest to prevent or delay its onset; advice for carers on helping dementia patients while protecting their own well-being; and stories of hope.
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