Polychlorinated biphenyl exposures and cognition in older U.S. adults: NHANES (1999-2002)

Polychlorinated biphenyls (PCBs) are ubiquitously present in humans because of their resistance to degradation and accumulation in fatty tissues. Data on neurotoxic effects in older adults are limited.

We examined the cross-sectional association between serum PCB concentrations and cognitive function in older adults from the general U.S. population.

We analyzed data from 708 respondents, 60-84 years of age, participating in the National Health and Nutrition Examination Survey (1999-2002). We used the summed concentrations of 12 lipid-standardized PCB congeners as the measure of exposure and assessed cognitive function with the Digit-Symbol Coding test. We adjusted analyses for age, education, race/ethnicity, and poverty/income ratio.

The median concentration of lipid-standardized PCBs in serum was 271 ng/g (interquartile range, 193-399 ng/g). We found a significant interaction between dioxin-like PCB concentration and age in association with cognitive score (p=0.04). Among older individuals (70-84 years of age), a 100-ng/g increase in serum concentrations of dioxin-like PCBs was associated with a significantly lower cognitive score (-2.7 points; 95% CI: -5.1, -0.2; p=0.04); however, in younger individuals (60-69 years of age), there was a nonsignificant positive association (2.9 points; 95% CI: -1.8, 7.7; p=0.32). Among the older participants, the negative association was more pronounced in women than in men.

Our findings support the hypothesis that PCB exposure has adverse cognitive effects even at levels generally considered to pose low or no risk, perhaps affecting mainly those of advanced age.