The Association Between The Combined Exposure Of Essential Trace Elements And Cognitive Function In Older Adults

ObjectiveSince China has become the country with the largest aging population in the world,cognitive decline among older adults in China has become a growing public health concern.There is no effective treatment for cognitive decline.Therefore,it is important to identify risk factors for cognitive decline to prevent or delay the onset of cognitive decline.Studies have shown associations between single essential trace elements（ETEs）and cognitive function in older adults.However,there is limited evidence on the effects of ETE mixture on cognitive function in older adults.This study aims to evaluate the associations of single ETEs and ETE mixture with cognitive function using a representative sample of community-dwelling older adults in China.MethodsA total of 6000 older adults aged 60 or above were selected using the probability proportional sampling（PPS）in eight districts or counties of Fuyang City,Anhui Province,China,from July to August 2018.In this study,questionnaires,physical measurements,and morning urine samples were collected.The Chinese version of the Mini-mental State Examination（MMSE）was used to measure cognitive function in older adults.The Inductively Coupled Plasma Mass Spectrometer（ICP-MS）was used to measure five essential trace elements（Selenium,Se;Vanadium,V;Cobalt,Co;Strontium,Sr;and Molybdenum,Mo）in urine.Multiple linear regression and Bayesian kernel machine regression（BKMR）models were performed to explore the associations of single ETEs and ETE mixture with cognitive function,respectively.ResultsA total of 3814 older adults with a mean age of 71.03±5.45 years were included in this study.Of all participants,1889（49.53%）were male and 1925（50.47%）were female.In addition,MMSE scores were 20.77±6.13 in this study.The detection rates of Se,V,Co,Sr,and Mo were greater than 99%,and the median concentrations of ETEs were15.66μg/g,1.68μg/g,0.31μg/g,163.68μg/g and 84.09μg/g,respectively.After adjusting for general demographic characteristics（gender,age,education,occupation,marital status,religious belief,and economic situation）,smoking status,alcohol consumption,physical activities,sleep quality,daily fruit intake,daily meat intake,hypertension,chronic kidney disease,daily activity capacity,and depression,single-element linear regression models found that Se[β=0.27,95%confidence interval（CI）:0.02 to 0.53]and V（β=0.23,95%CI:0.01-0.45）were positively associated with MMSE scores in older adults.After further adjusting for other ETEs,the multi-element linear regression models still found that Se（β=0.34,95%CI:0.05-0.63）and V（β=0.32,95%CI:0.01-0.62）were positively associated with MMSE scores in older adults.Considering the non-linear relationships between single ETEs and MMSE scores,we divided the five ETEs into quartiles for linear regression models and obtained similar results.After adjusting for similar covariates as described above,single-element linear regression models showed that the fourth quartile Se(β_Q4vs.Q1=0.58,95%CI:0.06-1.10)and V(β_Q4vs.Q1=0.52,95%CI:0.00-1.04)had higher MMSE scores compared with the first quartile.After adjusting for all covariates and other ETEs,multi-element linear regression models also showed that the fourth quartile Se(β_Q4vs.Q1=0.56,95%CI:0.01-1.12)and V(β_Q4vs.Q1=0.64,95%CI:0.03-1.25)had higher MMSE scores compared with the first quartile.BKMR models showed marginally positive associations of Se and V with MMSE scores.Moreover,higher urinary levels of ETE mixture were significantly associated with increased MMSE scores in a dose-response pattern,and Se was the most important contributor within the mixture.ConclusionSe and V are positively associated with cognitive function,individually and as a mixture.Higher urinary levels of ETE mixture are associated with increased cognitive function in older adults.Within this mixture,Se is the most important component.Considering that elements are always present simultaneously in the environment,mixture analyses rather than single ETE analyses may provide a real-world perspective on the relationship between ETE mixture and cognitive function.Further cohort studies are needed to clarify the association of multiple ETEs with cognitive function.