Associations Between Cadmium And Selenium Co-exposure And Cognitive Impairment Amongst Older Adults

ObjectiveTo investigate the prevalence of cognitive impairment and the levels of urinary cadmium and selenium amongst older adults aged 60 and above in Fuyang City,Anhui Province and analyze the associations between individual and combined exposure to cadmium and selenium and cognitive impairment.MethodsFrom June to August 2018,a total of 6,000 older adults aged 60 and above in Fuyang City,Anhui Province were selected using Probability Proportionate to Size Sampling(PPS)method.Questionnaires,physical examinations,and morning mid-stream urine were collected by trained investigators.The Chinese version of Mini-Mental State Examination(MMSE)was used to assess cognitive function.Inductively Coupled Plasma Mass Spectrometer(ICP-MS)was used to detect the concentrations of urinary cadmium and selenium.Univariate and multivariate logistic regression models were used to explore the relationships between urinary cadmium and selenium levels and cognitive impairment among the older adults.The dose-response curves of urinary cadmium concentration,selenium concentration with cognitive impairment were plotted by restricted cubic spline functions.Multivariate logistic regression model was used to explore the multiplicative interaction of cadmium and selenium on cognitive impairment.Relative excess risk due to interaction(RERI),attributable proportion due to interaction(AP),and synergy index(S)were used to evaluate the additive interaction of cadmium and selenium on cognitive impairment.ResultsThe study included 3814 older adults(1889 men and 1925 women).The prevalence of cognitive impairment was 36.5%.The detection rates of both urinary cadmium and selenium in the urine sample were 100%.Geometric mean and median values of cadmium concentration adjusted for creatinine were 1.00μg/g and 1.00μg/g.Geometric mean and median values of selenium concentration adjusted for creatinine were 14.88μg/g and 15.66μg/g.In multivariate logistic regression models,compared to the older adults with low exposure to urinary cadmium concentration(<0.79μg/g)adjusted for urinary creatinine,there was no statistical association between medium exposure to urinary cadmium concentration(0.80～1.25μg/g)and cognitive impairment(OR[95%CI]:1.09[0.91-1.30]),while a positive association between high exposure to urinary cadmium concentration(>1.25μg/g)and cognitive impairment(OR[95%CI]:1.20[1.01-1.43]).Meanwhile,a positive association between high exposure to urinary cadmium concentration(>1.25μg/g)and cognitive impairment was showed in older men(OR[95%CI]:1.39[1.08-1.78]).However,the association between cadmium exposure and cognitive impairment was disappeared amongst women.Multivariate logistic regression analysis showed that there was no statistical correlation between urinary selenium exposure and cognitive impairment amongst the older adults.Cadmium and selenium concentrations were divided into high and low exposure levels based on the median,with low exposure as the reference.In the overall population,univariate analysis showed a positive relation between high exposure to urinary cadmium and cognitive impairment(OR[95%CI]:1.17[1.02-1.33]),but this association was disappeared in the multivariate model.The interaction item of Cd and Se was statistically significant(Waldχ~2=4.112,P=0.043).After stratifying by selenium level,amongst the older adults with low exposure to urinary selenium,multivariate analysis found a positive association between urinary cadmium exposure and cognitive impairment(OR[95%CI]:1.38[1.12-1.71]).However,among the older adults with high exposure to urinary selenium,the association between urinary cadmium exposure and the cognitive impairment did not exist in both univariate and multivariate models.There was no additive interactions between cadmium and selenium(RERI[95%CI]:-0.19[-0.55-0.16];AP[95%CI]:-0.15[-0.42-0.12];S[95%CI]:0.61[0.26-1.31]).ConclusionThe prevalence of cognitive impairment was high amongst the older adults aged60 and above in Fuyang city.Urinary cadmium and selenium were detected in all the participants.Higher exposure to urinary cadmium was associated with an increased risk of cognitive impairment in older adults compared to those with lower exposure to urinary cadmium,whereas selenium exposure was not associated with cognitive impairment in older adults.Furthermore,there is an interaction between cadmium and selenium.A positive correlation between high cadmium exposure and cognitive impairment was found in older adults with low urinary selenium levels,but not in those with high urinary selenium levels.These results suggested that Se may protect against cognitive impairment by Cd.