Hypertension and Stroke Special Report
Blood Pressure and Brain Power
Johns Hopkins Health Alerts Hypertension (High Blood Pressure) and Stroke High Blood Pressure and Memory
High blood pressure (hypertension) is a known risk factor for vascular dementia (a condition caused by a series of tiny strokes that impair mental function and memory in older adults). Now a new study provides evidence of another link between high blood pressure and future mental decline. The study found that high blood pressure may play a role in the development of brain lesions that affect mental function.
Blood Pressure and the Brain
In a study in the Journal of the American Medical Association, researchers examined 3,657 people (age 65 to 102). People with higher blood pressures—a systolic blood pressure of 160 mm Hg or higher or a diastolic blood pressure of 90 mm Hg or higher—made more errors on tests of mental status than those with a systolic pressure between 130 and 139 mm Hg or a diastolic blood pressure between 70 and 79 mm Hg.The following year, a study in Hypertension examined mental function in 107 healthy people with moderate high blood pressure (averaging 164/89 mm Hg) and 116 people without hypertension (averaging 131/74 mm Hg). The average age of the participants in both groups was 76. On average, the group with high blood pressure had 10% slower reaction times on mental tests and was less able to remember words or numbers than the group without high blood pressure.
This study was the first to exclude other possible causes of mental decline, such as strokes, and to focus solely on the effects of high blood pressure. These findings echoed a 1995 study, which reported that each 10 mm Hg increase in systolic blood pressure is associated with a 9% greater risk of poor mental function.
More recently, a study in Psychology and Aging suggested that high blood pressure may be associated with white matter lesions (age-related changes that affect the brain’s ability to transmit information). These changes have been linked to declines in mental function, even in people without dementia. In the study, Scottish researchers tested mental function in 83 people in their late 70s and compared the results with similar tests that the participants took when they were 11 years old. Participants with the most white matter lesions had the greatest declines in mental function over time. In addition, people with high blood pressure had both a greater number of white matter lesions and a greater decrease in mental function than people with normal blood pressure.
How To Prevent Mental Decline
Clearly, evidence is mounting for a relationship between high blood pressure and decreased mental function. Exactly how high blood pressure might affect mental abilities, however, is still unknown. For example, mental deterioration may be due to hypertension-induced cerebral arteriosclerosis—hardening of the arteries in the brain that interferes with the delivery of blood (which contains vital oxygen and nutrients) to brain cells. A 1997 study linking high blood pressure to memory loss in the elderly found that people with high blood pressure had greater brain atrophy (as assessed by magnetic resonance imaging) than people with normal blood pressure. It seems likely that these two changes in the brain could be the basis of impaired mental function.Further research is necessary, however, to determine with certainty why and how high blood pressure and mental function are connected. Eventually, such an understanding could lead to new methods for preventing and treating mental decline in older adults.
In the meantime, some research has shown that treating high blood pressure during middle age helps to protect against mental deterioration in later years. A review article in the Journal of Neurological Sciences concluded that lowering blood pressure with antihypertensive drugs can reduce the risk of impaired mental function, and that calcium channel blockers and ACE inhibitors appear to be more effective than diuretics and beta-blockers for protecting mental function.
More research is also needed to examine the relationship between antihypertensive medication and mental function. Knowledge in this area is lacking because, until 1995, researchers focused on making sure blood pressure medication didn’t impair mental function (rather than on whether it could have a protective role). In general, control of blood pressure is the only established way to protect against the various complications related to high blood pressure.
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Posted in Hypertension and Stroke on May 7, 2006
