Lead author Michael Robbins, Ph.D., of the University of Maine, said the findings suggest that aggressive public health efforts to prevent, detect and control hypertension may help preserve cognitive abilities as well as cardiovascular health. "Even small reductions in blood pressure resulting from detection and treatment may preserve cognitive function for many Americans," he said.
The investigators analyzed data from the Maine-Syracuse Longitudinal Study obtained from residents of upstate New York who participated between 1976 and 2002. They studied questionnaires, medical interviews and physical examinations for 1,563 subjects, including 147 African-Americans.
The researchers used standard analytical and statistical tools to investigate correlations between blood pressure and cognitive functioning for a group of African-Americans and to compare these with findings for a group of whites. They also looked for relationships among age, blood pressure and cognition within these groups.
The investigators consistently observed significant associations of blood pressure to cognitive performance in the areas of abstract reasoning, psychomotor skills and visual organization skills.
For every incremental increase of 10 mm/Hg in the bottom (or diastolic) blood pressure number, the corresponding decrease in total cognitive performance for African-Americans was twice the magnitude of the decrease seen in whites. For systolic blood pressure (the top number), the decrease in cognitive performance of African-Americans was one and one-half times the magnitude of the decrease seen in whites.
The researchers found no significant differences between older and younger subjects.
These findings held even after the researchers made statistical adjustments for demographic, psychosocial and cardiovascular risk factors.
"This work is important," says Sheri Waldstein, Ph.D., director of the behavioral medicine graduate program at the University of Maryland, Baltimore County. "It demonstrates that the relation of higher blood pressure to lower levels of cognitive function is more pronounced among African-Americans than whites, even among non-demented persons, and that greater prevention and intervention efforts geared toward blood pressure reduction are needed.
"This may be particularly critical to the preservation of cognitive function among African-Americans," Waldstein adds.
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Robbins MA, et al. Blood pressure and cognitive function in an African-American and a Caucasian-American sample: the Maine-Syracuse study. Psychosomatic Medicine 67(5), 2005.