Abstract
BackgroundPolychlorinated biphenyls (PCBs) and metals (lead and cadmium) are neurotoxic and affect neurobehavioral performance. Yet little is known about the association between exposure to multiple neurotoxic compounds and cognitive functioning in older adults.MethodsUsing data from two consecutive cycles of the National Health and Nutrition and Examination Survey (1999–2002), path analysis was used to simultaneously evaluate the association between whole blood concentrations of 14 neurotoxic compounds and cognitive functioning measured by the Digit Symbol Coding Test of the Weschler Adult Intelligence Scale, 3rd Edition in participants 60–84 years of age (N = 498). Effect modification was assessed for age (above/below the mean) and sex.ResultsThe final path model fit 5 compounds (i.e. PCB 74, PCB 118, PCB 146, PCB 153, and lead). After controlling for co-exposures and confounders, PCB 146 (β = −0.16, 95% CI: −0.29, −0.02, p = 0.02) and lead (β = −0.10, 95% CI: −0.20, −0.006, p = 0.04) were negatively associated with DSC scores in 60–84 year olds. Whereas, PCB 153 was positively associated with DSC scores (β =0.20, 95% CI: 0.05, 0.35; p = 0.01).ConclusionsThis cross-sectional analysis which controlled for collinear exposure to several neurotoxic compounds demonstrated an association between non-dioxin like polychlorinated biphenyl exposure, specifically PCB 146, and lower cognitive functioning, in older adults. Lead exposure was also weakly associated with lower cognitive functioning. Additional studies are needed to determine the causality of the observed associations.
Highlights
Polychlorinated biphenyls (PCBs) and metals are neurotoxic and affect neurobehavioral performance
To eliminate outliers due to extreme age and to be consistent with previous studies [28] this sample consists of women and men aged 60–84 years of age who had their blood samples analyzed for lead, cadmium and polychlorinated biphenyls (PCBs) and completed the WAIS-III Digit Symbol Coding (DSC) module (n = 870)
Covariates We explored a variety of sociodemographic covariates based on prior literature showing that they were related to cognitive functioning and/or environmental chemical exposure including: race/ethnicity (Mexican American [MA], Other Hispanic [Other hispanic (OH)], Non-Hispanic White [Non-hispanic white (NHW)], NonHispanic Black [Non-hispanic black (NHB)]), age, education level, poverty income ratio (PIR) (≤0.99 and ≥ 1.00) and sex [28, 33,34,35]
Summary
Polychlorinated biphenyls (PCBs) and metals (lead and cadmium) are neurotoxic and affect neurobehavioral performance. Exposure to certain industrial chemicals such as lead, cadmium, and polychlorinated biphenyls (PCBs) can affect the central nervous system (CNS) and result in alterations in neurobehavioral performance [1,2,3]. There is evidence that the brain is vulnerable to environmental toxics during the later stages of life due to behavioral, metabolic and physiological changes that occur with aging [16]. These studies are often restricted to examining the effect of single environmental exposures on neurocognitive outcomes in older adults.
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