The relationship between high blood pressure and dementia

So, how does lowering high blood pressure reduce our risk of cognitive impairment and dementia? Most people who have dementia don’t have just a single cause. Two or even three different problems in the brain cause their cognitive impairment and lead to their decline in function. One study estimates that the fraction of dementia risk attributable to cerebrovascular disease — that is, strokes — was nearly 25% in people who developed significant memory loss late in life. These researchers also found that the dementia risk attributable to Alzheimer’s disease was considerably higher, nearly 40%.

My reading of the literature is that lowering blood pressure reduces dementia risk because it reduces the risk of stroke. It’s the strokes — not high blood pressure by itself — that cause cognitive impairment. Note, however, that the strokes may be so tiny that one doesn’t even know that they have them. But developing a lot of these tiny strokes (or a few big ones) will greatly increase our risk of dementia.

Optimal blood pressure for optimal brain health

Okay, but what’s considered a healthy blood pressure from the perspective of the brain? The SPRINT-MIND study answers that question: people are less likely to develop mild cognitive impairment if their systolic blood pressure is lower than 120 mm Hg compared to the control condition of between 120 and 140 mm Hg. Thus, for optimal brain health, it’s best to keep your systolic blood pressure below 120 mm Hg — at least according to the SPRINT-MIND study.

The bottom line

The take-home message is clear: You can reduce your risk of cognitive impairment and dementia by lowering your systolic blood pressure to less than 120 mm Hg, preferably with aerobic exercise, a Mediterranean diet, and a healthy weight, and by adding medications if those lifestyle changes alone are not sufficient.