High Blood Pressure Harms Memory and Shrinks Brains
A major threat to your brain as you get older is a stroke, often triggered by high blood pressure. Moreover, high blood pressure, even in the absence of a stroke, often inflicts subtle brain damage that can erode mental faculties.
High blood pressure today, memory loss tomorrow, is the message from recent research that links high blood pressure to damaged brain tissue, cognitive impairment, and “vascular dementia”—a decline in mental functioning, including memory, usually from vessel damage or mini-strokes.
In a 1998 study of 999 men, Swedish researchers at the Karolinska Hospital in Stockholm clearly documented that high blood pressure “can lead to cognitive impairment.” Men, now in their fifties, who had high blood pressure readings twenty years ago, showed the greatest decline in mental capacity and motor skills when recently tested. Men with the highest diastolic (lower number) blood pressure reading—over 105 mm/Hg—had the greatest mental impairment. Men with the lowest diastolic pressure—less than 70 mm/Hg—scored highest in thinking ability. Men whose high blood pressure had gone untreated suffered the most decline.
This study jibes with findings from an ongoing collaborative research at Stanford, UCLA, Indiana University, and Boston University. Researchers have tied high systolic (upper number) blood pressure in middle age to sharper declines in mental acuity after age sixty. For example men who had systolic pressure above 140 for twenty-five years exhibited twice as much intellectual decline as men with normal blood pressure. The suspected reason: The men had probably already experienced small undetected (silent) strokes induced by their high blood pressure.
HIGH BLOOD PRESSURE SHRINKS BRAINS
Indeed, high blood pressure can accelerate brain shrinkage as you age. This may help explain intellectual decline typical of old-age brain deterioration not caused by Alzheimer’s, according to researchers at the National Institute on Aging. They used brain imaging scans and neuropsychological tests to study people ages fifty-six to eighty-four, some with high blood pressure, others with normal blood pressure.
Investigators detected startling brain differences, even though none of the high blood pressure patients had ever had a stroke. The scans revealed that high blood pressure had taken a toll in increased brain atrophy in the temporal and occipital lobes that control memory and language. Those with high blood pressure also scored lower on language and memory tests than same-age individuals with normal blood pressure. “And the effect worsened with age,” said senior investigator Gene E. Alexander. The older the person, the worse the loss of brain matter and function. Unfortunately, taking drugs to control high blood pressure did not totally prevent detrimental brain changes.
More recently, Charles DeCarli, M.D., associate professor of neurology and director of the Alzheimer’s Disease Center at the University of Kansas, used magnetic resonance imaging (MRI) to document that midlife high blood pressure speeds up aging and shrinkage of the brain, increasing risk of stroke in late life.
He tracked 414 individuals, starting when they were average age forty-seven for about twenty-five years. Specifically, he found that those with high blood pressure in midlife had smaller brains, more abnormal white matter (specific nerve tissue in the brain), and a higher risk of stroke, including silent strokes, in old age. Such “silent strokes” occur in the tiny blood vessels of the brain without symptomatic fanfare, but over time result in subtle progressive damage, usually detectable only by an MRI. (About 12 percent in his study showed signs of silent strokes on brain imaging.) Further, “the higher your blood pressure, in midlife, the worse the outlook for old age—the smaller your brain, the more extensive the white matter damage and the greater the expected intellectual impairment,” says Dr. DeCarli.
Distressingly, even borderline high blood pressure at midlife predicted greater brain atrophy in old age. Dr. DeCarli worries that many middle-aged people who appear healthy may, in fact, have borderline high blood pressure that is slowly, but surely, sabotaging their brains. So potentially devastating is the damage that he urges everyone with even borderline high blood pressure to find ways to reduce it.
“People with high blood pressure are four times more apt to have a stroke.”—Dr. Philip Wolf, professor of neurology, Boston University
Even slight blood pressure elevations may help precipitate a stroke. Indeed, Boston University investigators recently found in a study of 566 people over a forty-year period that half of the strokes occurred in those with high normal (defined as 130-139 mmHg systolic, the top number) or mildly high blood pressure (140-159 mmHg systolic).
What about caffeine? Dr. Jack E. James, LaTrobe University, Melbourne, Australia, says that coffee increases blood pressure in the population on average by 2 to 4 mm Hg. Thus, cutting out caffeine, he predicts, could reduce stroke risk by 17 to 24 percent.