Association between Serum Iron, Blood Lead, Cadmium, Mercury, Selenium, Manganese and Low Cognitive Performance in Old Adults from National Health and Nutrition Examination Survey (NHANES): A Cross-Sectional Study.

Abstract

Cognitive decline is a public health problem for the world's aging population. This study was to evaluate the relationships between serum iron, blood lead, cadmium, mercury, selenium, and manganese and cognitive decline in elderly Americans. Data of this cross-sectional study was extracted from the National Health and Nutritional Examination Survey (NHANES 2011-2014). Cognitive performance was measured by the consortium to establish a registry for Alzheimer's disease (CERAD), Animal fluency, and digit symbol substitution test (DSST) tests. Weighted univariable and multivariate logistic regression analyses were used to assess the associations between six trace elements and low cognitive performance, with odds ratios (ORs) and 95% confidence intervals (CIs). Subgroup analyses based on diabetes and hypertension history were further assess the associations. A total of 2,002 adults over 60 years old were included. After adjusting covariates, elevated serum iron levels were associated with the decreased risk of low cognitive performance (OR=0.995, 95%CI: 0.990-0.999), as well as in the elderly without diabetes history (OR=0.992, 95%CI: 0.988-0.997) and with hypertension history (OR=0.993, 95%CI: 0.988-0.997) in the Animal Fluency test. High blood cadmium and blood manganese levels were associated with the odds of low cognitive performance in old adults with diabetes (OR=2.900, 95%CI: 1.311-6.417) and hypertension (OR=1.037, 95%CI: 1.009-1.066) history, respectively. In the DSST test, high blood lead levels were related to the odds of low cognitive performance (OR=1.102, 95%CI: 1.019-1.192), as well as in the elderly without diabetes (OR=1.126, 95%CI: 1.026-1.235) and hypertension (OR=1.121, 95%CI: 1.002-1.255) history. Elevated blood cadmium levels were connected with low cognitive performance in diabetic (OR=3.177, 95%CI: 1.323-7.27) and hypertensive (OR=1.896, 95%CI: 1.056-3.403) old people. High blood selenium levels were linked to the decreased risk of low cognitive performance in all the elderly (OR=0.987, 95%CI: 0.981-0.993). Appropriate iron, selenium supplementation and iron-, selenium-rich foods intake, while reducing exposure to lead, cadmium and manganese may be beneficial for cognitive function in the elderly.