ABSTRACT
Objective To explore the correlation between environmental selenium(Se) levels and cognitive ability among rural elderly population, and the effect of Se on cognitive skill of the elderly. Methods Two study sites(Zichuan district and Gaomi city of Shandong) with different environmental Se levels were selected according to rural elderly people ≥ 65 years were extracted by stratified random sampling method in each site. A retrospective survey was carried out using dietary intake questionnaire for the elderly for the past 1 year, and their daily total Se intake was calculated. Questionnaire was also used to obtain cognitive skill information in the elderly people. The Community Screening Instrument for Dementia, the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) Word List Learning Test, the Indiana University (IU) Story Recall Test, the Animal Fluency Test, and the IU Token Test were applied to assess the cognitive ability. Se level in these samples was analyzed. Correlation between the Se levels of environment and those of human body were analyzed statistically. Results There were 0.163), (0.405 ± 0.086)]mg/kg and nail Se[(147.44 ± 17.42), (117.38 ± 22.48)μg/L]between the two groups (U = 31.59, 25.00, 23.67, all P ＜ 0.01 ). There were positive correlation among the nail Se, environmental Se and Se in all subjects(r = 0.51,0.46, 0.60, all P ＜ 0.01 ). The differences of the CSID total score, the CERAD Word List Learning Test, the CERAD Word List Recall Test and the IU Story Recall Test between the two sites were statistically significant(F = 2.56, 9.18, 7.48, 4.42, all P ＜ 0.05), excluding the Indiana University Story Recall Test.After eliminating possible confounding factors, the Se levels and the CSID total score, the IU Story Recall Test, the Animal Fluency Test and the IU Story Token Test had a significantly positive correlation (r = 0.076, 0.138, 0.042,0.107, P ＜ 0.05 or ＜ 0.01 ), excluding the CERAD Word List Learning Test. Conclusions This study supports the hypothesis that a life long low Se level is associated with lower cognitive ability. The cognitive abilities in the elderly population lived in areas with high environmental selenium levels are significantly higher than that of the elderly lived in areas with low environmental selenium levels.
ABSTRACT
Objective To investigate selcnium(Se) levels of environment and human body in Gaomi City and Zichuan District of Shandong. Methods Lijiaying Township in Gaomi City of Weifang City, Zhaili Township and Longquan Township in Zichuan District of Zibo City were selected. Two farming soil samples at different spot, local wheat and corn, residents nail samples from 3 to 4 families were collected in each natural village in the investigated towns. The contents of Se were detected by 2,3-diamino naphthalene fluorescence method. Results Se level of the soil, wheat, corn, and nails in Lijiaying [(0.054 ± 0.019), (0.022 ± 0.009), (0.018 ± 0.007), (0.365 ± 0.108)mg/kg] was significantly lower than that in Zhaili [(0.425 ± 0.080), (0.130 ± 0.043), (0.098 ± 0.026), (0.751 ± 0.134)mg/kg] and Longquan[(0.487 ± 0.153), (0.112 ± 0.030), (0.097 ± 0.029), (0.735 ± 0.145)mg/kg;P < 0.01]. In Lijiaying, Se was deficient in soil, wheat, corn(< 0.200, < 0.025 mg/kg), above Se deficiency diagnosis and below Se-adequate level in the nail, while in Zhaili and Longquan, the Se level in the soil (0.425, 0.487 mg/kg), wheat(0.130, 0.112 mg/kg), corn (0.098, 0.097 mg/kg), nails (0.751, 0.735 mg/kg) was adequate (≥0.400 mg/kg). Conclusions The external environment is Se-deficient in Lijiaying, Se-adequate in Longquan and Zhaili. The selenium level in human body is consistent with the external environment.