Neuro-Cognitive Function of Polychlorinated Biphenyls (PCBs) Exposed Elderly in Taiwan

Autor: Kao-Chang Lin, 林高章
Rok vydání: 2004
Druh dokumentu: 學位論文 ; thesis
Popis: 92
Introduction: Polychroninated biphenyls (PCBs) and dibenzofurans(PCDF) have lipophilic character and are known to affect central nervous system functioning. In 1979 Yucheng (oil disease) episode, approximately 2000 people in central Taiwan were exposed to PCBs and PCDFs, with fatigue, skin manifestations, liver diseases, and other symptoms. The exposed mothers delivered offspring with dark skin, delayed developmental milestones, and poorer neuro-cognitive functioning. The neuro-cognitive effects of such exposure are unknown in elderly people, who are more vulnerable in the neuro-cognitive functioning. Objective: 1). To compare the neuro-cognitive and memory functioning between PCBs/PCDFs exposed elderly and the control group; 2). To determine the association between gender and neuro-cognitive functioning; 3). If neuro-cognitive functioning is affected in the exposed people, whether dose-response relation exists; 4). To determine whether biochemical markers and thyroid hormones are affected in exposed people, and 5) To determine whether effects on thyroid function mediated the neuro-cognitive effects of PCBs/ PCDFs. Methods: Retrospective cohort in community at Central Taiwan from the outbreak in 1979 was conducted in those aged 60 years or older in exposed and matched controls. Questionnaire and neuropsychological Test in Chinese version were done by trained interviewers. Basic information, Mini-Mental Status Examination (MMSE), Digit symbol (DS), Attention and Digit Span (ADS), Verbal memory of Recall Trials, Delay recall in 30 minutes, Learning Ability of Wechsler Adult Intelligence Scale (WAIS), Visual Memory Span of Wechsler Memory Scale-Revised (WMS-R), Geriatric Depression Scale-Short Form(GDS-SF), Activity of Daily Life (ADL), and Luria’s Motor and Tactile Performance were included in the study. Results:166 (57%) exposed and 162 (61%) controls completed the tests with mean age 69.9±5.8years, male to female 49:51, and education in 4.3±3.5 years. Exposed people had reduced functioning in ADS (Forward, p=0.0002), VMS (Backward, p=0.02), Learning Ability (p=0.03), and trending in delay recall in 30 minutes, Verbal Memory Recall Trials (p=0.06), and similar MMSE (P=0.12), Motor (p=0.49), Sensory (p=0.70), Depression (p=0.99), DS (p=0.09) and ADL (p=0.35) scores. Women scored lower in MMSE, DS, ADS-backward and VMS as compared to men. Comparing to the exposure levels of PCBs, ADS showed significant linear trend. Although T3 levels were found in exposed subjects (p=0.0002), the neuro-cognitive effects were not mediated by the reduced T3 levels. Discussion: The results were similar to Shantz’s study that PCBs had learning and memory deficits in exposed humans. A high incidence of depressive mood was found in 82% of the subjects and warranted further investigation. Some dose-response relationship was found, but mainly trends only. Lacking of the exposure levels of PCDFs prohibited more thorough dose-response evaluation. Conclusion: Our study showed neuro-cognitive deficits in certain aspect of attention, visual memory and learning ability in elderly people previously exposed to PCBs, and found dose-response relationship in these impairments. It provides direct evidence that exposure to PCBs/PCDFs had effects on neuro-cognitive functioning and therefore minimizing exposure by measures, for environmental protection, is warranted.
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