Reading vs. lead poisoning

Good reading ability may help protect the brain from damage linked to toxic lead, a new study suggests.

Lead was found to be 2.5 times more likely to have negative effects on the brains of adults with limited reading ability than on the brains of good readers, the researchers report in the July 31 issue of Neurology.

However, reading ability did not protect individuals' motor skills from the toxic effects of lead.

How the study was conducted
A team at the Centre for Occupational and Environmental Neurology, in Baltimore, studied the effects of lead exposure on 112 lead smelter workers in New Brunswick, Canada. The workers took several thinking and motor-speed tests, as well as a measure of their reading ability.

The researchers then calculated working lifetime lead exposure from historic blood lead levels obtained by the smelter. The workers were divided into groups with "high cognitive reserve" - defined as a reading level of 12th grade or higher - and "low cognitive reserve," a reading level of 11th grade or lower.

Cognitive reserve refers to the mental abilities, such as reading ability, that are generally not affected by lead exposure in adulthood. They act as a measure of the brain's ability to maintain function despite damage.

Bad readers hit harder
The results: "Even though the two groups had similar lead exposure, the cognitive effects of lead were 2.5 times greater in workers with low reading ability," study author Dr Margit L. Bleecker said in a prepared statement. "In contrast, the effect of lead on motor speed was comparable in both groups as cognitive reserve does not apply to motor speed," she said.

"This suggests that high cognitive reserve has a protective effect that allowed these workers to maintain their functioning, even though lead affected their nervous system as shown by its effect on their motor skills," Bleecker added.

How might reading protect the brain? According to the researchers, an increased number of cortical synapses in larger brains might provide more brain capacity, the option to use alternative brain circuits if some are damaged, and the ability to process tasks more efficiently. – (HealthDayNews)

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August 2007