Nov. 17 (UPI) -- People exposed to lead during childhood shows signs of reduced brain development -- and lower IQs -- well into adulthood, a study published Tuesday by JAMA found.
The analysis of 564 adults with documented lead exposure at age 11 revealed that their IQ scores declined two points for every 5 micrograms per deciliter -- a little over 3 ounces -- of the substance in their blood, the data showed.
Study participants at age 11 years had an average of roughly 11 mcg. per deciliter of lead in their bloodstream, the researchers said. Lead levels of above 5 mcg. per deciliter are considered above normal, according to the U.S. Centers for Disease Control and Prevention.
The lower IQ was attributed to lessened brain development caused by lead exposure, the researchers said.
"By now we know quite well that children exposed to lead experience disrupted brain development -- with commensurate implications for cognitive ability, emotion regulation and fine motor skills -- but we did not know what the implications of this disrupted brain development would be over time," study co-author Aaron Reuben told UPI.
"The generation of children exposed to peak levels of lead, during the peak era of leaded gasoline, are entering midlife and old age [and] we need to intervene if we want to lower [their] risk of degenerative brain disease," said Reuben, a doctoral candidate in clinical psychology at Duke University.
Up to 20% of all children age 2 and younger have been found to have higher-than-normal, and potentially unhealthy, levels of lead in their blood, according to the CDC.
Research has linked high levels of lead exposure in childhood to IQ deficits and early-onset dementia later in life, Reuben and his colleagues said.
For this study, the researchers from Duke University analyzed data from participants in the Dunedin Study, a project that tracks the physical and mental health of people in Dunedin, New Zealand, who were born between April 1, 1972 and March 31, 1973.
They measured the structural brain integrity of the study participants at age 45 using magnetic resonance imaging.
For every 5 mcg. per deciliter of lead in their blood at age 11, study participants had an average of 1.19 square centimeters -- about a quarter of an inch -- less surface area in their cerebral cortex at age 45, according to the researchers.
The cerebral cortex, also called gray matter, is the outer layer of the brain and is responsible for thinking, perceiving, producing and understanding language.
Study participants with higher lead exposures also showed signs of lower hippocampal volume. The hippocampus of the brain plays a key role in learning and memory.
"Our findings reinforce the importance of eradicating lead from children's environments [because] the implications for brain health and function are lifelong, at least up to middle-age, and may in fact worsen over time," Reuben said.
"This should add credence and importance to the costly efforts to abate lead risks in neighborhoods with old homes, schools with leaded pipes and communities with lead-enriched soils," he said.