The most serious effects of untreated hypertension are well known: strokes, heart attacks, heart failure, kidney disease, and vision loss. But hypertension can contribute to lesser-known health conditions, including cognitive (thinking) impairments. In this Health Alert, Johns Hopkins explains how hypertension leads to thinking problems and provides advice.
Hypertension, particularly in mid-life, may be a major risk factor for cognitive decline, dementia, and Alzheimer's disease. On the plus side, research is showing that treating hypertension may lower the risk.
How does hypertension lead to thinking problems? One obvious reason is that high blood pressure increases the risk of stroke by damaging blood vessels that carry blood to the brain. This damage leads to the buildup of plaques, and when one of these plaques ruptures, a blood clot forms. If this blood clot cuts off blood supply to brain cells responsible for memory or other cognitive functions, the death of these cells can lead to impairments in thinking ability.
But researchers are starting to find that hypertension has a more insidious effect on the brain -- that is, you don't need to have a full-blown stroke for hypertension to do its damage. Brain scans show that individuals with hypertension are more likely to have brain lesions, called white matter hyperintensities (WMHs), than people with normal blood pressure. And the greater the number of these WMHs, the higher the risk of cognitive problems like dementia and Alzheimer's disease.
So what are WMHs, and how do they affect your thinking? Your brain has two layers: an outer layer of gray matter that is packed with brain cells that process information, and an inner layer of white matter that contains nerve fibers that transmit information between brain cells. Hypertension-related buildup of plaque reduces blood flow to nerve fibers in the white matter, and the insufficient blood flow causes decay of the nerve fibers' myelin sheaths, which are necessary for transmittal of information.
What can you do? Research indicates that gaining control of your blood pressure can reduce your risk of dementia. There is also some evidence that lowering blood pressure reduces the occurrence of new WMHs. The study looked only at people who were taking an ACE inhibitor in combination with a thiazide diuretic. But those taking this drug combination had fewer and smaller new WMHs after three years than those who received a placebo. More research is needed, however, to find out whether other blood pressure medications have the same effect.
