September 13, 2006
Older adults exposed to high levels of lead before the 1980s are showing signs of problems with memory and thinking as a result of long-term lead exposure in their communities, a new study reports. The findings were published in the online edition of Neurology, the scientific journal of the American Academy of Neurology.
The study involved 985 adults living throughout the city of Baltimore, Maryland. The participants were between the ages of 50 and 70 years and had been exposed to higher levels of lead prior to the 1980s, when lead had been used extensively in commercial products like paint.
Researchers tested the amount of lead in the tibia, or shinbone, since lead accumulates in bone. They also gave participants a battery of tests that measured language, processing speed, eye-hand coordination, executive functioning, verbal memory and learning, and visual memory.
The study found that higher lead levels in the bones were consistently associated with worse cognitive performance on tests. "The analysis showed that the effect of community lead exposure was equivalent to the decline in memory function seen in two to six years of aging," said principal investigator Brian Schwartz, M.D., of the Johns Hopkins Bloomberg School of Public Health in Baltimore.
In addition, the study found lead levels were significantly higher in African Americans compared to Caucasians. Researchers say the difference likely represents the long-term higher environmental lead exposures sustained by African Americans in the United States, but could also be due to different bone mineral densities in African Americans compared to Caucasians.
The findings are consistent with a study earlier this year that found that people who worked in factories using lead had small areas of damage in their brains years later. In that study, more than a third of the factory workers had damage to the white matter of their brains, an area critical for thinking and memory.
Long-term lead exposure, particularly in children, has long been linked to problems with thinking and memory. The researchers did not address whether damage caused by lead exposure increases the risk of Alzheimer's. The researchers did suggest that damage due to lead exposure may make the brain more vulnerable to changes associated with Alzheimer's disease, and thus cause the outward symptoms of Alzheimer's to occur earlier in life.
In addition to its inclusion in household products like paint, lead was included in gasoline until the 1970s and emitted in large amounts into the air. Many of those who grew up before the late 1970s still carry high lead levels in their bodies.
More studies are needed to explore the potential effects on public health caused by lead and other environmental toxins. For more on Alzheimer's risk factors, visit www.ALZinfo.org.
Online edition, Neurology, September 13, 2006. The American Academy of Neurology.