NEURO-COGNITIVE CHANGES IN ELDERLY EXPOSED TO PCBS AND PCDFS IN TAIWAN

Abstract

ISEE-117 Introduction: Polychlorinated biphenyls (PCBs) and dibenzofurans (PCDFs) are known to affect central nervous system functioning. In 1979’s outbreak episode, 2061 people in central Taiwan were exposed to PCBs/PCDFs, and presented with fatigue, skin manifestations, liver diseases and other symptoms. The exposed mothers delivered offspring with delayed developmental milestones and poorer neuro-cognitive function. Such central cognitive effects are unknown in vulnerable elderly people. Objective: 1) To compare the cognitive and memory function between exposed and control group; 2) To determine the association between gender and cognitive state; 3) To investigate whether a dose-response relation exists; 4) To study whether biochemistry and thyroid hormones are affected in exposed subjects; and 5) To determine whether thyroid function mediated the neuro-cognitive effects of PCBs/PCDFs exposure. Methods: A retrospective cohort study was conducted in exposed and matched controls, aged ≥60 years old. Neuropsychological tests included Mini-Mental Status Examination (MMSE), Digit Symbol (DS), Attention and Digit Span (ADS), Verbal memory of Recall Trials, 30-minute Delay recall and Learning Ability of Wechsler Adult Intelligence Scale-Revised and Visual Memory Span (VMS) of Wechsler Memory Scale-Revised. Additionally, Geriatric Depression Scale-Short Form (GDS-S), Activity of Daily Life (ADL), and Luria’s Motor and Tactile Performance were studied. Results: 166 (57%) exposed and 162 (61%) control subjects completed tests. The mean age was 69.9±5.8years, the male to female ratio was 49:51, and mean duration of education was 4.3±3.5 years. Exposed people had reduced functioning in ADS-forward (p=0.0002), ADS-total (p=0.001), VMS-backward (p=0.05), VMS-total (p=0.04), Learning Ability (p=0.03), trial 4 and 5 of verbal recalls (p=0.02) and trend in Delay Recall and Recall Trials (p=0.06). No difference was noted in MMSE (p=0.12), Motor (p=0.49), Sensory (p=0.70), Depression (p=0.89), DS (p=0.07) and ADL (p=0.29). Women scored lower in MMSE, DS, ADS-forward, ADS-backward, ADS-total, VMS-forward, VMS-backward, and VMS-total, as compared to men. ADS-forward showed significance in post-hoc PCBs stratification. With regard to thyroid function, although abnormal T3 were found in exposed groups (p=0.0002), the neuro-cognitive effects were not mediated by the reduced T3 levels. Discussion: Our results were similar to Schantz’s study of certain memory and learning deficits in the elderly. Although no gender and dosing effect was seen in the Michigan cohort study due to small sample size, our data showed these effects. Conclusion: Our study showed neuro-cognitive deficits in certain aspects of attention, visual memory and learning ability in the elderly people previously exposed to PCBs. A dose-response effect was obvious in these impairments. In the exposed group, women scored lower than men. Low T3 levels are significant but unrelated to cognition. This study provided evidence that exposure to PCBs/PCDFs has central cognitive effects, both in the elderly and in children. All efforts to minimize response to PCBs/PCDFs are warranted.