Impairments of Memory and Learning in Older Adults Exposed to Polychlorinated Biphenyls via Consumption of Great Lakes Fish

Statistical Issues

In this study multiple statistical tests were performed on multiple cognitive outcomes, and only a few significant effects of contaminant exposure were observed. This raises the possibility that the significant findings were spurious associations. We believe that this is unlikely because four chemicals, PCBs, DDE, mercury, and lead, were evaluated as exposure variables, but all of the significant negative associations were related to PCB exposure. Also, several aspects of cognitive functioning including memory and learning, executive function, and visual--spatial function were assessed, but all of the negative effects were seen on the tests of verbal memory and learning. Children exposed to PCBs in utero via maternal consumption of Great Lakes fish also showed impairments, primarily on tests involving verbal and memory function (1-4). Despite these consistencies, it would be prudent to interpret the findings with caution until they have been replicated in an independent exposure cohort.

Conclusions

This study is the first to find that adults exposed to elevated levels of PCBs may be at risk of neuropsychological impairment. The results should be important in the risk assessment arena because current fish consumption advisories focus heavily on protecting the pregnant woman and fetus. As with children exposed in utero, certain aspects of verbal memory and learning seem to be the primary targets for PCB-related impairments in older adults. Executive, visual--spatial, and motor (13) function did not appear to he affected. Furthermore, other neurotoxic contaminants in the fish including DDE, mercury, and lead did not have any negative impact on cognitive or motor function. It is possible, however, that subtle changes in other outcomes or those related to other contaminants were missed because the modest sample size restricted statistical power. It is also possible that greater exposure to PCBs and/or these other contaminants would result in additional impairments. For example, workers exposed to PCBs in capacitor manufacturing plants have been reported to have serum PCB levels 10- to 100-fold higher than the levels that are typical in Great Lakes fish eaters (3,7). These workers may be at considerably greater risk of neuropsychological impairments than are Great Lakes fish eaters, and are a group that warrants further study.

REFERENCES AND NOTES

(1.) Jacobson SW, Fein GG, Jacobson JL, Schwartz PM, Dowler JK. The effect of intrauterine PCB exposure on visual recognition memory. Child Dev 56:853-860 (1985).

(2.) Jacobson JL, Jacobson SW, Humphrey HEB. Effects of in utero exposure to polychlorinated biphenyls and related contaminants on cognitive functioning in young children. J Pediatr 116:38-45 (1990).

(3.) Jacobson JL, Jacobson SW, Padgett R, Brumitt G, Billings R. Effects of prenatal PCB exposure on cognitive processing efficiency and sustained attention. Dev Psychol 28:297-306 (1992).

(4.) Jacobson JL, Jacobson SW. Intellectual impairment in children exposed to polychlorinated biphenyls in utero. N Engl J Med 335:783-789 (1996).