Having hypertension in midlife (ages 40 through 60) is associated with elevated risk of cognitive impairment and Alzheimer’s dementia later in life, even more so than having the so-called Alzheimer’s gene.
“It is clear that cerebral vascular disease”—that is, hardening of the arteries inside our brain—“and cognitive decline travel hand in hand,” something I’ve addressed before. “However, the independent association of AD [Alzheimer’s disease] with multiple AVD [atherosclerotic vascular disease] risk factors suggests that cholesterol is not the sole culprit in dementia.”
As I discuss in my video Higher Blood Pressure May Lead to Brain Shrinkage, one of the most consistent findings is that elevated levels of blood pressure in midlife, ages 40 through 60, is associated with elevated risk of cognitive impairment and Alzheimer’s dementia later in life—in fact, even more so than having the so-called Alzheimer’s gene.
“The normal arterial tree”—all the blood vessels in the brain—“is…designed as both a conduit and cushion.” But when the artery walls become stiffened, the pressure from the pulse every time our heart pumps blood up into our brain can damage small vessels in our brain. This can cause “microbleeds” in our brain, which are frequently found in people with high blood pressure, even if they were never diagnosed with a stroke.
These microbleeds may be “one of the important factors that cause cognitive impairments,” “perhaps not surprising[ly],” because on autopsy, “microbleeds may be associated with [brain] tissue necrosis,” meaning brain tissue death.
And speaking of tissue death, high blood pressure is also associated with so-called lacunar infarcts, from the Latin word lacuna, meaning hole. These holes in our brain appear when little arteries get clogged in the brain and result in the death of a little round region of the brain. Up to a quarter of the elderly have these little mini-strokes, and most don’t even know it, so-called silent infarcts. But “no black holes in the brain are benign.” As you can see at 2:12 in my video, it’s as though your brain has been hole-punched.
“Although silent infarcts, by definition, lack clinically overt stroke-like symptoms, they are associated with subtle deficits in physical and cognitive function that commonly go unnoticed.” What’s more, they can double the risk of dementia. That’s one of the ways high blood pressure is linked to dementia.
There’s so much damage that high blood pressure levels can “lead to brain volume reduction,” literally a shrinkage of our brain, “specifically in the hippocampus,” the memory center of the brain. This helps explain how high blood pressure can be involved in the development of Alzheimer’s disease.
As you can see at 3:02 in my video, we can actually visualize the little arteries in the back of our eyes using an ophthalmoscope, providing “a noninvasive window” to study the health of our intracranial arteries, the little vessels inside our head. Researchers “found a significant association” between visualized arterial disease and brain shrinkage on MRI. However, because that was a cross-sectional study, just a snapshot in time, you can’t prove cause and effect. What’s needed is a prospective study, following people over time. And that’s just what the researchers did. Over a ten-year period, those with visual signs of arterial disease were twice as likely to suffer a significant loss of brain tissue volume over time.
What can we do about high blood pressure? A lot! See, for example:
What else can we do to forestall cognitive decline or dementia? I referenced my video Alzheimer’s and Atherosclerosis of the Brain earlier, and here are other videos that offer information on treatment and prevention:
Michael Greger, M.D.
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