Lead Exposure Plus Hypertension May Cause Cognitive Decline

Lead exposure and high blood pressure are associated with cognitive impairments in older adults. And being exposed to lead early in life may have a long-term effect on cognitive ability and motor function that carries through to adulthood, the researchers suggest.

The study results were to be presented Saturday at the American Heart Association's annual high blood pressure conference, in Washington, D.C.

"Many of the things that happen with age are not just a byproduct of age," said lead author Dr. Domenic Sica, a professor of medicine and pharmacology at Virginia Commonwealth University. "Your catalog of diseases and exposures comes back to haunt you over time. Lead exposure probably carries a long-term determinative function on some of the changes that occur with hypertension" -- another name for high blood pressure.

Lead is associated with a greater risk of hypertension and also with a greater tendency to chronic kidney disease, Sica said.

Using data from the Third National Health and Nutrition Survey (NHANES III), Sica's team found that lead exposure early in life, combined with high blood pressure in working-age adults, may lead to diminishing cognitive abilities in later life.

NHANES III involved 4,835 people ages 20 to 59. Of these, 51 percent were female, 35.4 percent were white, 31.4 were percent black and 29.7 percent were Hispanic.

The researchers looked at the relationships involving pulse pressure, blood lead level and C-reactive protein -- a marker of inflammation. They also looked at the results of neurobehavioral tests and simple reaction-time tests.

There was a correlation between blood pressure and these measures, Sica said. In neurobehavioral tests, which included measures of reaction time, the researchers found slower and less stable reaction time associated with increases in pulse pressure and blood lead levels.

"We have to be more careful in understanding the impact of blood lead levels," Sica said.

One expert finds the study results too preliminary to draw definitive conclusions.

"It may be that environmental conditions conducive to lead exposure independently harm brain function," said Dr. David L. Katz, an associate professor of public health and director of the Prevention Research Center at Yale University School of Medicine. "Such conditions might include poverty during childhood or adverse environmental conditions."

More work is needed to determine if lead exposure and blood pressure combine to form a unique threat to the brain, Katz said. "Given the prevalence of these exposures and the intense public interest in strategies to forestall dementing diseases, such efforts will be awaited with impatience."

Another expert thinks the findings point to a serious public health problem.

The impact of lead on cognitive function has been well known, and the impact of high blood pressure on cognitive function is also well known. "The fact these two may be synergistic is not a surprise," said Hillel W. Cohen, an associate professor of epidemiology and public health at Albert Einstein College of Medicine in New York City.

"This is more evidence to address lead in the environment and blood pressure as well," he said.

More information

The American Heart Association can tell you more about high blood pressure.