MONDAY, Sept. 29, 2003 (HealthDayNews) -- The effects of high blood pressure on mental function in older people are more subtle than has been believed, a carefully controlled laboratory study finds.
"This challenges the conventional wisdom that high blood pressure and aging interact to affect cognitive function," says study author David Madden, a professor of medical psychology at Duke University Medical Center. "They do interact in more complex ways than we currently understand."
The study, which included people with uncontrolled high blood pressure but without any disease, shows the importance of other conditions such as diabetes or heart disease on mental function, he adds.
"While the changes in cognitive performance associated with elevated blood pressure seen in our experiments were statistically significant, they are unlikely to interfere with mental functioning during everyday life," Madden says. "However, the changes we recorded in the laboratory may represent a situation that could become clinically significant when other diseases, especially those that are cardiovascular in nature, are included."
The Duke experiment, whose results are reported in the Sept. 29 issue of Aging, Neuropsychology and Cognition, included 96 volunteers. Half had high blood pressure for which they were not taking medication. The other half had blood pressure brought down to healthy levels by blood therapy.
Sitting at computers, the volunteers did a visual search test in which they were shown a pair of letters and then had to tell whether those letters were present in another, larger display. A different sequence of letter displays was used to test their memory.
Looking at the results by age, Madden reports that high blood pressure slowed mental function only in middle-age participants, aged 40 to 59. High blood pressure did not dim the performance of the oldest participants, aged 60 to 79.
Most previous studies along these lines have looked only at people with high blood pressure who had other illnesses, Madden notes. "Our goal was to determine if there was an effect of elevated blood pressure on the natural course of healthy people," he says.
The results do not support the classical belief that high blood pressure causes deterioration of mental function in all older people, he says. "You must consider both a person's age and disease condition."
The laboratory results do not show that some older people can safely disregard their high blood pressure, Madden says, because "it is relatively rare to have high blood pressure by itself." Even if uncontrolled high blood pressure does not affect thinking ability, it is a major risk factor for heart disease and stroke, he says.
He is continuing to study the complex effects of high blood pressure on thinking. "The significance of these cognitive effects will become more clear as additional evidence is obtained regarding the changes in brain structure," the journal report says.