"We know that in general, hypertension increases with age," Madden said. "Our goal was to determine if there was any effect of elevated blood pressure on the natural course of healthy aging."
For their experiments, the Duke team recruited 96 adult volunteers 48 with unmedicated high blood pressure and 48 with normal blood pressure. The patients were then equally divided into three groups: young (20-39), middle-aged (40-59) and older (60-79). Blood pressures were taken at regular intervals throughout the course of the experiments.
The tests, which were taken on a personal computer, measured how quickly participants could correctly respond in two general areas visual search tasks and memory search tasks. In both cases, the stimuli on the computer screen were different combinations of 20 white consonants on a black background.
For the visual search tasks, participants had to view a pair of letters, and then after a period of time, had to quickly determine which one of that pair was present within displays of four to six letters. For the memory task, participants viewed either four or six letters, and then after a period of time, two letters appeared on the screen. Participants had to indicate which one of the letters was within the original group. Each participant underwent 640 trials.
"The results of our experiments show that the interaction between the effects of blood pressure and adult age do not support the predictions of the classical model, which holds that increasing blood pressure accelerates the decline in intelligence tasks," Madden said. "Our analysis of response times found that a decline in the high blood pressure group was only evident for the middle-aged group, but not for the youngest or oldest participants."
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Contact: Richard Merritt
merri006@mc.duke.edu
919-684-4148
Duke University Medical Center
29-Sep-2003