Oct. 25, 2000 ST. PAUL, MN - Lead exposure on the job can cause progressive declines in memory and learning abilities nearly two decades later, according to a study in the October 24 issue of Neurology, the scientific journal of the American Academy of Neurology.
The study compared 535 former chemical manufacturing employees exposed to lead at work to 118 non-exposed people from the same neighborhoods.
"The effects of the average level of bone lead found in former lead workers was like five more years of aging on the brain," said Brian Schwartz, MD, of Johns Hopkins School of Hygiene and Public Health in Baltimore, MD.
The study participants were followed for four years, undergoing two to four sets of neurological tests with an average of one year between tests. The former workers had an average of 8 years of occupational exposure to lead with an average of 16 years since last working with lead.
The first year of the study, lead levels were determined through blood tests, while follow up visits measured lead levels in bone through a technique called x-ray fluorescence.
"The higher the peak level of lead determined in former lead workers, the greater the decline in brain functions," Schwartz said. "Since these declines were seen long after exposure to lead had stopped, it suggests that the effect of lead on the brain is progressive."
The workers not only had greater declines in test scores due to lead, but also in normal age-related declines in brain functions, Schwartz said.
Significant differences were discovered between the former workers and other participants in tests involved in visual construction, verbal memory and learning, visual memory, planning and organizational ability, and manual dexterity.
"We know there's a decline in brain power as we get older -- generally we call this 'normal aging,'" said Schwartz. "Most of the research has been about how chemicals, like lead, affect kids. This is the first study to explore long-term problems caused by exposure to chemicals as adults. Some of what we have been calling 'normal aging' may in fact be due to past exposures to chemicals or other agents that can affect the central nervous system. This is potentially a very important health problem."
The American Academy of Neurology, an association of more than 16,000 neurologists and neuroscience professionals, is dedicated to improving patient care through education and research. A neurologist is a medical doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system.
For more information about the American Academy of Neurology, visit its Web site at http://www.aan.com. For online neurological health and wellness information, visit NeuroVista at http://www.aan.com/neurovista.
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