Lead Exposure Plus High Blood Pressure May Impair Mental Ability

"Both lead exposure and hypertension have been associated withcognitive impairments in older adults. Lead exposure early in life mayhave a long-term effect on cognitive ability and motor function, andhave a carry-through effect in adult life," said lead investigatorDomenic Sica, M.D., professor of Medicine and Pharmacology at VirginiaCommonwealth University, Richmond.

Preliminary findings from this epidemiological analysis of theThird National Health and Nutrition Survey (NHANES III) indicate thatthe interaction between lead exposures early in life combined with highblood pressure in working age adults may lead to diminishing cognitiveabilities in later life.

"These findings suggest a possible additive or synergisticeffect between blood pressure levels and blood lead load on theaccuracy and time taken to perform a mental task involvingconcentration, in working age adults in the general population," Sicasaid.

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

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 werepercent Black and 29.7 percent were Hispanic.

"The interaction of pulse pressure and blood lead levels onperformance of the digit task was significant after controlling forother variables," Sica said. "There was an inverse relationship betweenthe mental tests and the highly significant and adverse effects onperformance of the digit task pulse pressure, blood lead level, andC-reactive protein."

Other neurobehavioral tests included measures of reaction timeand reaction time variance. Results suggested slower and less stablereaction time associated with increases in pulse pressure and bloodlead levels.

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

The aging process alone does not lead to automatic decline incognitive ability. It can happen, however when the aging process isassociated with hypertension and the presence of other diseases and/orenvironmental exposures to factors such as lead exposure, Sica said.

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

Co-author is Stephen Harkins, Ph.D.