Abstract
BACKGROUND: 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. OBJECTIVE: We examined the cross-sectional association between serum PCB concentrations and cognitive function in older adults from the general U.S. population. METHODS: 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. RESULTS: 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. CONCLUSION: 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.