- A long-term study investigated over 500 people in a small town in New Zealand, all of whom had childhood lead exposure
- Researchers conducted MRI scans on the participants at age 45
- Results revealed the presence of significant changes in brain structure and cognitive deficits among the study participants
People in the small town of Dunedin, New Zealand, underwent decade-long research by scientists at Duke University. Researchers investigated 1,037 people born between 1972 and 1973, with a history of childhood lead exposure. Only 997 of these participants remained alive till the age of 45.
564 of the original participants received lead testing at 11 years of age and therefore, remained part of the longitudinal study. Researchers then conducted MRI (magnetic resonance imaging) scans on the participants and assessed their brain’s structural integrity. Cognitive tests along with subjective reports helped researchers collect information on cognitive performance.
Our findings involve gross features of how your brain looks as a whole. Our research started by looking at these features of the brain because scientists don’t really know a whole lot about childhood lead exposure and the brain later in life.
Terrie Moffitt, senior author
Childhood Lead Exposure Caused Lower IQs
The hippocampus – part of the brain responsible for memory, learning, and emotions – was found to have a lower volume in the participants. Furthermore, researchers discovered a drop of 2 IQ points by age 45 for every 5 micrograms per deciliter more lead the participant had as a child.
Additionally, those with the highest childhood lead exposure also demonstrated deficits in the white matter of the brain. This is the part of the brain largely responsible for transmitting messages across the brain.
We find that there are deficits and differences in the overall structure of the brain that are apparent decades after the exposure. And that’s important because it helps us understand that people don’t seem to recover fully from childhood lead exposure and may, in fact, experience greater problems over time.
Aaron Reuben, co-first author
Interestingly, the participants did not report any loss in cognitive abilities despite their friends and family stating otherwise. According to their friends and family, the participants struggled with their memory and had attention deficits.
Long-Term Effects
Till the 1980s, leaded gasoline was widely used across the world. However, inhalation of fumes from vehicles led to elevated blood lead levels among children. This resulted in impaired neurological development in children. According to the Centre for Disease Control and Prevention (CDC), there are no safe blood lead levels in children. Levels of 5 μg/dL should prompt medical investigations. 94% of the participants in the Dunedin Study had blood lead levels above 5 mcg/dL at age 11.
While the effects of lead on children’s health are widely studies, not a lot is known about its long-term impact. The Dunedin Study has managed to find evidence of childhood lead exposure causing lower structural brain integrity in midlife.
Researchers hypothesize that the white matter changes can result in dementia, later on, however, it is too early to tell whether or not that can happen. As more changes can occur with age, doctors will likely follow-up with the patients to measure their risk of degenerative diseases.
Reference:
Reuben A, Elliott ML, Abraham WC, et al. Association of Childhood Lead Exposure With MRI Measurements of Structural Brain Integrity in Midlife. JAMA. 2020;324(19):1970-1979. doi:10.1001/jama.2020.19998
