[Association between cognitive impairment and main metals among oldest old aged 80 years and over in China].

Objective: To identify the main metals involved in cognitive impairment in the Chinese oldest old, and explore the association between these metal exposures and cognitive impairment. Methods: A cross-sectional study was conducted on 1 568 participants aged 80 years and older from Healthy Aging and Biomarkers Cohort Study (2017 to 2018). Fasting venous blood was collected to measure the levels of nine metals (selenium, lead, cadmium, arsenic, antimony, chromium, manganese, mercury, and nickel). The cognitive function of these participants was evaluated by using the Chinese version of the Mini-Mental State Examination (CMMSE). The random forest (RF) was applied to independently identify the main metals that affected cognitive impairment. The multivariate logistic regression model and restricted cubic splines (RCS) model were used to further verify the association of the main metals with cognitive impairment. Results: The age of 1 568 study subjects was (91.8±7.6) years old, including 912 females (58.2%) and 465 individuals (29.7%) with cognitive function impairment. Based on the RF model (the out-of-bag error rate was 22.9%), the importance ranking of variables was conducted and the feature screening of five times ten-fold cross-validation was carried out. It was found that selenium was the metal that affected cognitive function impairment, and the other eight metals were not included in the model. After adjusting for covariates, the multivariate logistic regression model showed that with every increase of 10 μg/L of blood selenium levels, the risk of cognitive impairment decreased (OR=0.921, 95%CI: 0.889-0.954). Compared with the lowest quartile(Q1) of blood selenium, the ORs (95%CI) of Q3 and Q4 blood selenium were 0.452 (0.304-0.669) and 0.419 (0.281-0.622) respectively. The RCS showed a linear dose-response relationship between blood selenium and cognitive impairment (Pnonlinear>0.05). Conclusion: Blood selenium is negatively associated with cognitive impairment in the Chinese oldest old.目的： 识别中国高龄老人认知功能损伤的主要金属，分析主要金属暴露与认知功能损伤的关联。 方法： 对中国老年健康生物标志物队列研究（2017—2018年）中1 568名年龄80岁及以上的研究对象开展横断面研究。采集空腹静脉血检测研究对象血液中九种金属（硒、铅、镉、砷、锑、铬、锰、汞和镍）的水平，使用中国版本的简易认知功能量表评估研究对象的认知功能。应用随机森林模型识别对认知功能损伤影响主要的金属，并采用多因素logistic回归模型和限制性立方样条（RCS）模型进一步识别主要金属和认知功能损伤之间的关系。 结果： 1 568名研究对象的年龄为（91.8±7.6）岁，其中女性912名（58.2%），认知功能损伤者465名（29.7%）。基于随机森林模型（袋外错误率为22.9%）对变量进行重要性排序并进行五次十折交叉验证特征筛选后发现，对认知功能损伤影响的金属为硒，其他8种金属未能纳入模型。在调整协变量后，多因素logistic回归模型分析结果显示血硒水平每提高10 μg/L，认知功能损伤的风险有降低趋势（OR=0.921，95%CI：0.889~0.954）；与血硒Q1组相比，Q3和Q4组的OR（95%CI）值分别是0.452（0.304~0.669）和0.419（0.281~0.622）。RCS模型显示，血硒与认知功能损伤存在线性剂量-反应关系（P非线性>0.05）。 结论： 血硒与中国高龄老人认知功能损伤呈负向关联。.