The Association Between The Internal Exposure Levels Of Selenium And Cognitive Impairment Among Chinese Older Adults

Objective:The cognitive impairment of older adults has attracted extensive attention from researchers at home and abroad,and the global socio-economic impact of its disease burden is increasing.As an essential trace element,selenium plays an important role in growth,development and nervous system regulation.In this study,the data of older adults from 31 provinces in China was used to explore the association between the internal exposure levels of selenium and cognitive impairment among Chinese older adults,so as to provide scientific basis for the prevention and treatment of cognitive impairment in older adults,strengthen the health concern and intervention of high-risk groups.Methods:Relying on the"China National Human Biomonitoring Program",this study selected older adults aged 60-79 years old,and included a total of 3424 respondents after excluding the missing individuals with key information.Blood and urine selenium concentrations were measured by inductively coupled plasma mass spectrometry.Cognitive function was measured by Mini-Mental State Examination（MMSE）,and cut-off points were adjusted according to education level.Multi-stage stratified sampling was used to ensure that the data was adequately representative.Using frequency and composition ratio to describe of count data;usingc² inspection to compare the rate between groups;the concentration of selenium in blood and urine was not normally distributed,and was expressed by geometric mean value（GMS）and95%confidence interval（95%CI）.Missing values are filled by multiple interpolation.Logistic regression model was used to investigate the association between selenium concentrations in blood and urinary and cognitive impairment.To investigate the effect of different selenium concentrations on cognitive impairment,the selenium concentrations in blood and urine were divided into quintules（Q ₁,Q₂,Q₃,Q₄,Q₅）,and Q ₁ group was used as the reference.A restricted cubic spline model was used to further explore the dose-response association between selenium exposure and cognitive impairment.In further subgroup analysis,older adults were stratified by age（60-69,70-79 years）and sex（male and female）.Results:（1）The prevalence of cognitive impairment in the population was 19.0%,including 21.3%in females and 15.9%in males.In univariate analysis,there were significant differences in age,gender,residence,smoking,hair coloring,and whether nuts were used in the past year between the cognitively impaired and the cognitively normal population.No significant differences were found in BMI,marital status,alcohol consumption,central obesity,anemia,hypertension,and diabetes.（2）Multivariate logistic regression model showed that the OR value and 95%CI of the risk of cognitive impairment were 0.94（0.90-0.99）for each 10μg/L increase in blood selenium concentration.Compared with older adults in Q₁ group,the risk of cognitive impairment was lower in Q₄and Q₅ groups,with OR values and 95%CI of0.53（0.35-0.83）and 0.60（0.37-0.97）,respectively.No statistical association was found between urinary selenium concentration and the risk of cognitive impairment in older adults.（3）Restricted cubic spline model showed that there was a linear dose-response association(P _nonlinear=0.075)between the blood selenium concentrations and risk of cognitive impairment in older adults.With the increase of blood selenium concentrations,the risk of cognitive impairment in the elderly continued to fall.When blood selenium concentrations was more than 160μg/L（OR=0.75,95%CI:0.60-0.94）,the risk tends to be stable;when the blood selenium concentrations was more than 187μg/L（OR=0.70,95%CI:0.49-1.00）,the association with cognitive impairment in older adults without statistical significance.There was a nonlinear dose-response association(P _nonlinear<0.001)between urinary selenium concentration and the risk of cognitive impairment in older adults.The risk of cognitive impairment in older adults decreased with the increase of urinary selenium concentration,and remained stable when urinary selenium concentration exceeded 40μg/L（OR=0.75,95%CI:0.65-0.85）.There was no statistically significant association between urinary selenium concentration above 92μg/L（OR=0.82,95%CI:0.67-1.00）and cognitive impairment in older adults.（4）Stratified analysis results showed that higher selenium concentrations were significantly associated with better cognitive function in older adults in different age and different gender groups.For the subjects aged 60-69 years,compared with older adults in the Q₁ group,older adults in the Q₄ group had a lower risk of cognitive impairment,with OR value and 95%CI of 0.48（0.29-0.79）;For subjects aged 70 to79 years,those in the Q₅ group had a lower risk of cognitive impairment compared to those in the Q₁ group,with an OR value and 95%CI of 0.43（0.22-0.85）.For men,the risk of cognitive impairment was lower in the Q₂and Q₄ groups compared to the Q₁group,with an OR value of 0.52（0.30-0.88）and a 95%CI of 0.37（0.18-0.75）,respectively.For women,older adults in the Q₅ group had a lower risk of cognitive impairment compared to those in the Q₁ group,with an OR value and 95%CI of 0.59（0.36-0.99）.There were gender differences in the association between urinary selenium concentration and cognitive impairment in older adults.Higher urinary selenium concentration was associated with better cognitive function in older adults in women,but not in men.For women,compared with older adults in the Q₁ group,the risk of cognitive impairment was lower in the Q₂,Q₃,Q₄ and Q₅ groups,with OR values and 95%CI of 0.58（0.36-0.92）,0.56（0.35-0.89）,0.51（0.31-0.82）and 0.59（0.36-0.98）,respectively.（5）Sensitivity analysis showed that the association between selenium concentration and cognitive impairment remained after adjustment for education,multiple interpolation,and stroke.Without considering the effect of education level on MMSE score,the OR value and 95%CI of cognitive impairment were 0.95（0.91-0.99）for every 10μg/L increase in Se concentration.Compared with the elderly in the Q₁group,the risk of impaired cognitive function was lower in the Q₃ and Q₄ groups,with OR values and 95%CI of 0.58（0.39-0.85）and 0.66（0.41-1.06）,respectively.After the effect of multiple interpolation was excluded,the OR value and 95%CI of the risk of cognitive impairment were 0.93（0.87-0.99）for every 10μg/L increase in Se concentration.Compared with the elderly in the Q₁ group,the risk of impaired cognitive function was lower in the Q₄ and Q₅ groups,with an OR value of 0.47（0.29-0.78）and a 95%CI of 0.53（0.30-0.94）,respectively.After controlling for stroke,the OR and 95%CI for each 10μg/L increase in selenium concentration was 0.94（0.90-0.99）for the risk of cognitive impairment.Compared with the elderly in the Q₁group,the risk of cognitive impairment was lower in the Q₄ and Q₅ groups,with OR values and 95%CI of 0.56（0.36-0.87）and 0.61（0.38-1.00）,respectively.No significant association was found between urinary selenium concentration and cognitive function in older adults.Conclusion:（1）Higher blood selenium concentration was associated with better cognitive function in the elderly,while no significant association was found between urinary selenium concentration and cognitive function in older adults.（2）There was a linear dose-response association between blood selenium concentration and cognitive impairment,and a nonlinear dose-response association between urine selenium concentration and cognitive impairment.（3）Stratified analysis showed that higher selenium concentrations were significantly associated with better cognitive function in older adults in different age and gender groups;there were gender differences in the association between urinary selenium concentration and cognitive impairment in older adults.Higher urinary selenium concentration was associated with better cognitive function in women group,but not in men.（4）Sensitivity analysis Adjusting for education,multiple interpolation,and stroke,higher selenium concentrations were still associated with better cognitive function in older adults,confirming the robustness of the results of this study.