Lead exposure plus high blood pressure may impair mental ability

September 24, 2005

Exposure to lead in early childhood and adolescence may contribute to hypertension-related decline that can impair a person's cognitive abilities, according to a new study presented at the 2005 American Heart Association's High Blood Pressure Research meeting.

"Both lead exposure and hypertension have been associated with cognitive impairments in older adults. Lead exposure early in life may have a long-term effect on cognitive ability and motor function, and have a carry-through effect in adult life," said lead investigator Domenic Sica, M.D., professor of Medicine and Pharmacology at Virginia Commonwealth University, Richmond.

Preliminary findings from this epidemiological analysis of the Third National Health and Nutrition Survey (NHANES III) indicate that the interaction between lead exposures early in life combined with high blood pressure in working age adults may lead to diminishing cognitive abilities in later life.

"These findings suggest a possible additive or synergistic effect between blood pressure levels and blood lead load on the accuracy and time taken to perform a mental task involving concentration, in working age adults in the general population," Sica said.

To determine cognitive function, researchers used the digit symbol substitution, a complex test of mental abilities that considers time and accuracy in completing the task. Using data from NHANES III, researchers looked at the relationships of pulse pressure, blood lead level, and C-reactive protein, a marker of inflammation. Neurobehavioral tests and simple reaction time tests were also assessed.

NHANES III involved 4,835 people ages 20 to 59, (average 35.8). Fifty-one percent were female, 35.4 percent were Caucasian, 31.4 were percent Black and 29.7 percent were Hispanic.

"The interaction of pulse pressure and blood lead levels on performance of the digit task was significant after controlling for other variables," Sica said. "There was an inverse relationship between the mental tests and the highly significant and adverse effects on performance of the digit task pulse pressure, blood lead level, and C-reactive protein."

Other neurobehavioral tests included measures of reaction time and reaction time variance. Results suggested slower and less stable reaction time associated with increases in pulse pressure and blood lead levels.

Additional findings suggested that socio-economic status and/or nutritional status may influence the accumulation of lead in the body, and may mediate the interaction between lead load and pulse pressure on cognitive performance in middle-aged adults, researchers said.

The aging process alone does not lead to automatic decline in cognitive ability. It can happen, however when the aging process is associated with hypertension and the presence of other diseases and/or environmental exposures to factors such as lead exposure, Sica said.

"There's a need to better understand the relationships between blood pressure and blood lead levels," he said. "This study may invigorate researchers to further investigate these relationships."

Co-author is Stephen Harkins, Ph.D.
-end-
Statements and conclusions of study authors that are published in the American Heart Association scientific journals are solely those of the study authors and do not necessarily reflect association policy or position. The American Heart Association makes no representation or warranty as to their accuracy or reliability.

NR05 - 1112 (HYP MEETING05/Sica)

American Heart Association

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