Association between serum iron concentrations and cognitive impairment in older adults aged 60 years and older: A dose-response analysis of National Health and Nutrition Examination Survey

Abstract

Epidemiological evidence on peripheral iron and cognitive impairment in older adults is sparse and limited. Results on serum iron and cognitive impairment in older adults from the National Health and Nutrition Examination Survey have not been reported. Data on serum iron and cognitive impairment from individuals ≥ 60 years of age were obtained from the 2011–2014 NHANES (N = 3,131). Serum iron concentrations were determined with DcX800 method. Cognitive impairment was assessed with four cognitive tests: the Digit Symbol Substitution Test (DSST), the Animal Fluency (AF), the Consortium to Establish a Registry for Alzheimer’s Disease Delayed Recall (CERAD-DR) and Word Learning (CERAD-WL) tests. Logistic regression and restricted cubic splines were adopted to explore the dose-response relationship between serum iron concentrations and cognitive impairment. Comparing the highest to lowest tertile of serum iron concentrations, the multivariate-adjusted odds ratios of scoring low on the DSST were 0.70 (0.49–1.00), 0.88 (0.65–1.20) for CERAD-WL, 0.65 (0.48–0.88) for CERAD-DR, and 0.78 (0.53–1.15) for AF. Stratified analyses by sex showed that the above-mentioned associations were mainly found in men; however, the interaction with sex was not significant. Dose-response analysis showed that relationships between serum iron and cognitive impairment evaluated by DSST and CERAD-DR were linear, respectively.

Mushroom intake and cognitive performance among US older adults: the National Health and Nutrition Examination Survey, 2011–2014

“…Multivariable linear regression models (proc surveyreg; SAS institute) with appropriate sampling weight, cluster and strata were used to examine the association of mushroom consumption with each cognitive function in its original continuous scale (CERAD-WL, CERAD-DR, AF and DSST scores), adjusting for potential confounders including age, sex, ethnicity-race, education, family poverty to income ratio, smoking status, physical activity, alcohol intake, total energy intake, history of CVD, history of diabetes and the HEI-2015 score. We also applied multivariable logistic regression models using the SAS surveylogistic procedure to examine the association of mushroom consumption with low cognitive function using the cutoff scores of < 14 for AF, < 34 for DSST, < 17 for CERAD-WL and < 5 for CERAD-DR (32,33) adjusting for the same covariates mentioned above. Imputation was performed for participants with missing demographics, lifestyle and self-reported diseases variables using the fully conditional specification method (43) .…”

“…Presently, there is no gold standard cutoff point to assess low cognitive performance using the CERAD-WL, CERAD-DR, AF and DSST tests. Thus, as done by recently published studies using the same NHANES data, low cognitive performance for the present study was defined using the cutoff scores of < 14 for AF, < 34 for DSST, < 17 for CERAD-WL and < 5 for CERAD-DR (32,33) .…”

Level-specific associations of urinary antimony with cognitive function in US older adults from the National Health and Nutrition Examination Survey 2011–2014

“…For CERAD, AFT, and DSST results, there is currently no gold standard cut-off point for detecting impaired cognitive performance. To highlight different forms of cognitive performance, we used the lowest quartile of each test score in the study group as a cut-off, which is consistent with earlier published literature [ 35 ].…”

Relationships between urinary metals concentrations and cognitive performance among U.S. older people in NHANES 2011–2014

“…For CERAD, animal fluency, and DSST outcomes, there is currently no gold standard cut-off threshold; however, prior research ( 26 ) utilizing the NHANES database identified persons in the study group with the lowest score in the quartile as cognitively impaired. As a result, the 25th percentile was chosen as the threshold for poor cognitive function in this study.…”