Blood pressure—related cognitive decline occurs in younger as well as older persons, according to recent research published in Hypertension (2004;44:1-6). The results indicate that pathophysiologic processes that adversely affect the brain “may begin earlier in the adult lifespan than previously thought,” according to the researchers.
They studied 529 participants from the Maine-Syracuse Longitudinal Study of Hypertension, each of whom was given the Wechsler Adult Intelligence Scale and a hypertension diagnostic examination at baseline. The subjects were followed over 20 years, during which time the relationship between blood pressure and cognitive decline was examined for two age groups (18 to 46 years and 47 to 83 years).
Baseline blood pressure was unrelated to crystallized/verbal, memory, and speed performance measures of the intelligence scale. In both the younger and older age groups, however, systolic, diastolic, and mean arterial pressure at enrollment and the blood pressure categories created by the Seventh Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) predicted the decline in visualization/fluid abilities. Visualization/
fluid abilities were measured using picture completion, picture arrangement, block design, and object assembly tests.
The levels of decline with higher levels of blood pressure were not such that they interfered with everyday functioning; “in fact, one can decline from a very high level of ability to a lower level ability and still perform above the average,” said the study’s lead author, Penelope K. Elias, PhD, from the Department of Psychology, University of Maine, Orono. She notes that moving from a “normal” blood pressure classification to “stage I hypertension” would result in an estimated 8.12% decrement in correct responses on the visual/fluid component of the intelligence scale over 20 years.
“Younger adults were generally less affected by hypertension than older adults, but the higher the blood pressure, the greater the change in cognitive performance over time for both young adults and older adults,” she said. “Thus, youth is not a protection against very subtle but progressive decline in cognition in relation to blood pressure level.”
She continued, “Our work is also important because it is now believed that some individuals continue beyond mild decline in cognitive performance to catastrophic change, such as dementia. Thus, prevention of high blood pressure is important at all ages.”
At the population level, lowering blood pressure by 20 mm Hg systolic or 10 mm Hg diastolic, or from “hypertensive” to “normal” classification under the JNC definition, would have a “considerable beneficial effect on the preservation of cognitive abilities in the population as a whole,” the authors write.
Whether or not cognitive changes can be reversed with antihypertensive drug therapy should be studied in clinical trials, they believe. “Our feeling is that preventing the rise in blood pressure over time is the critical aspect of protecting cognitive functioning from the ravages of sustained untreated high blood pressure,” said Dr. Elias.