(HealthDay News) – Occupational exposure to chemical solvents affects the cognitive abilities of less-educated workers, but not more-educated workers, with a dose-response relationship between lifetime exposure and the risk of poor cognition.

Erika L. Sabbath, ScD, from Harvard University in Boston, and colleagues analyzed data from a prospective cohort of 4,134 French national gas and electricity employees. A validated job-exposure matrix was used to assess lifetime exposure to chlorinated solvents, petroleum solvents, benzene, and non-benzene aromatic solvents. Education was classified as less than secondary-education or above secondary education, and was considered a proxy for cognitive reserve. Scoring below the 25th percentile on the Digit Symbol Substitution Test was used to define cognitive impairment.

The researchers found that less-educated patients had higher solvent exposure rates, with a dose-response relationship between lifetime exposure to each solvent type and an increased relative risk for poor cognition (eg, high exposure to benzene: relative risk, 1.24). Significant trends were seen for three of the four solvents. Among less-educated patients, the recency of solvent exposure also predicted worse cognition. Among those participants with secondary education or higher, quantification of solvent exposure was not significantly associated with cognition.

“Solvent exposure is associated with poor cognition only among less-educated individuals,” the authors write. “Higher cognitive reserve in the more-educated group may explain this finding.”

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