Correlation between environmental selenium levels and cognitive ability among rural elderly population

：Objective To explore thecorrelation between environmental selenium(Se) levels and cognitive ability among ruralelderly population, and the effect of Se on cognitive skill of the elderly. Methods Twostudy sites(Zichuan district and Gaomi city of Shandong) with different environmental Selevels were selected according to rural elderly people ≥ 65 years were extracted by stratified random sampling method in each site. Aretrospective survey was carried out using dietary intake questionnaire for the elderlyfor the past 1 year, and their daily total Se intake was calculated. Questionnaire wasalso used to obtain cognitive skill information in the elderly people. The CommunityScreening Instrument for Dementia, the Consortium to Establish a Registry for Alzheimer'sDisease (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 cognitiveability. Se level in these samples was analyzed. Correlation between the Se levels ofenvironment and those of human body were analyzed statistically. Results There were0.163), (0.405 ± 0.086)]mg/kg and nail Se[(147.44 ± 17.42), (117.38 ± 22.48)μg/L]betweenthe two groups (U = 31.59, 25.00, 23.67, all P ＜0.01 ). Therewere 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 ofthe CSID total score, the CERAD Word List Learning Test, the CERAD Word List Recall Testand 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 IndianaUniversity Story Recall Test.After eliminating possible confounding factors, the Se levelsand the CSID total score, the IU Story Recall Test, the Animal Fluency Test and the IUStory 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 WordList Learning Test. Conclusions This study supports the hypothesis that a life long low Selevel is associated with lower cognitive ability. The cognitive abilities in the elderlypopulation lived in areas with high environmental selenium levels are significantly higherthan that of the elderly lived in areas with low environmental selenium levels. Key words: Aged; Selenium; Cognitive ability