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.