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Effects of childhood lead exposure carry over into old age, researchers find

Cognitive functioning is worse in older adults who were exposed to lead contamination during childhood, new research suggests. File photo by Molly Riley/UPI
Cognitive functioning is worse in older adults who were exposed to lead contamination during childhood, new research suggests. File photo by Molly Riley/UPI | License Photo

Nov. 9 (UPI) -- Cognitive functioning is worse in older adults who were exposed to lead contamination during childhood than in those who were not exposed, new research suggests.

The study, which found no association between childhood lead exposure and the rate of cognitive decline, appeared Wednesday in Science Advances, a journal of the American Association for the Advancement of Science.

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The Flint, Mich., water crisis from 2014 to 2016 reignited concern about lead toxicity in drinking water, which can cause permanent damage in the developing brains of children, but much less is known about its long-term consequences, the scientists said.

The new findings have widespread implications since an estimated 170 million Americans alive today -- more than half of the U.S. population -- were exposed to high levels of lead as children, the researchers said.

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"Our findings are also germane to public health concerns about American children born during the 1960s, 1970s and 1980s, who were exposed to historically unprecedented levels of lead via leaded gasoline and other sources," the scientists said in their paper.

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"These cohorts had blood lead levels, on average, three times the current reference value [a measurement used to identify children with blood lead levels higher than most children's levels] and within the next 10 to 20 years, they will enter ages at which dementia risk is heightened."

This creates an urgent need for more research to better understand the lifelong implications of childhood lead exposure on brain aging and find effective interventions to mitigate long-term damage among people at high risk, the researchers said.

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Haena Lee, the study's first author, is an assistant professor in the Department of Sociology at Sungkyunkwan University, Seoul, South Korea. Previously, she was a postdoctoral scholar in the University of Southern California's Davis School of Gerontology in Los Angeles.

Co-authors of the study, which was funded by the National Institutes of Health's National Institute on Aging, are affiliated with the University of Minnesota and Northwestern University.

The research team explored the long-term association between childhood lead exposure and trajectories of cognitive change in late life among respondents to the Health and Retirement Study.

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Using this nationally representative sample of U.S. older adults, the investigators analyzed cognitive tests repeatedly taken by participants from 1998 to 2016.

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Then, the scientists examined linked data from 1940 U.S. census records to pinpoint where those participants lived as children. The study included 1,089 older adults with varying degrees of past lead exposure who were living in 398 different cities as children.

The investigators found that older adults who lived as children in cities with lead pipes and acidic or alkaline water -- the conditions required for lead to leach into drinking water -- had worse cognitive functioning, but not steeper cognitive decline.

Compared to people who weren't exposed to lead in drinking water as children, the lead-exposed group had significantly higher levels of many risk factors thought to be important for cognitive decline, including lower levels of education, less household income and a higher prevalence of heart disease.

The study's results suggest that about one-third of the association between childhood lead exposure and later-life cognition is accounted for by the person's level of educational attainment, the scientists said.

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