Comparing Mini‐Mental State Examination and Attention and Digit Span in elderly exposed to polychlorinated biphenyls and polychlorinated dibenzofurans

Background: Polychlorinated biphenyls (PCB)/polychlorinated dibenzofurans (PCDF) are known to affect central nervous functioning. In recent studies, elderly patients who have been exposed to these have been noted to have psychological deficits. There is little known about which test is sensitive to neurotoxins in cognitive evaluation. The objective of the present study was to compare the significance between selective psychological tests in cognitive assessment in PCB‐laden elderly. Methods: A retrospective PCB/PCDF exposed cohort was observed. Exposed elderly aged ≥60 years and registered in Central Health Administration were enrolled, and similar age‐ and sex‐matched subjects served as non‐exposed controls. The Mini‐Mental State Examination (MMSE) and Attention and Digit Span (ADS) were tested in both groups. Student's t‐test, χ²‐test and linear regression models were used for statistical analysis. Results: A total of 165 exposed patients and 151 controls were analyzed. The exposed group included 49% men, a mean age of 69.3 ± 6.4 years and an education level of 4.0 ± 3.9 years. The controls included 52% men, a mean age of 69.9 ± 5.5 years and an education level of 4.5 ± 3.2 years. There was no statistical difference in MMSE before and after adjusting for the confounding variables of age, sex and education (P= 0.16 vs P= 0.12). However, ADS‐forward and ADS‐total scores showed a significant decline in the exposed subjects (P= 0.0001 vs P= 0.001). Using a linear regression among stratified PCB and cognitive functioning (≤30 ppb; 31–89; ≥90), a dose effect was found at the medium (31–89 ppb) and high exposure (≧90 ppb) levels. Conclusion: Our observations showed attention and short‐term memory were impaired in PCB‐laden elderly patients. Higher exposure level showed lower cognitive functioning in ADS. The MMSE was insensitive to neurotoxins. The present study shows that the selective test has a decisive role in toxic‐related cognitive assessments.