Relationships between trace elements vanadium, cobalt, copper, strontium, and molybdenum levels in urine and cognitive impairment in elderly men in an area of Guangxi

Background  Previous studies have shown that the homeostasis imbalance of trace elements vanadium (V), cobalt (Co), strontium (Sr), and molybdenum (Mo) may lead to physiological abnormalities and even diseases in human body, but there are few studies about their effects on the cognitive function of the elderly so far.

Objective  The study aims to explore the relationships of urinary levels of V, Co, Copper (Cu), Sr, and Mo with cognitive impairment among elderly men in an area of Guangxi.

Methods  From August 2016 to July 2017, a total of 375 elderly men aged 60 years and above were recruited from an area of Guangxi. Basic information was collected by questionnaire, and cognitive function was evaluated by the Chinese version of Mini-Mental State Examination (MMSE). At the same time, their urine samples were collected, and urinary concentrations of V, Co, Cu, Sr, and Mo were detected by inductively coupled plasma mass spectrometry (ICP-MS). Wilcoxon rank sum test was used to compare urinary trace elements levels of participants with different cognitive levels. A general linear model was utilized to evaluate the relationship between urinary trace elements levels and MMSE scores. The participants were divided into T₁, T₂, and T₃ groups according to each trace element's tertile concentrations, and then a binary logistic regression model was conducted to analyze the relationships between trace element levels and cognitive impairment.

Results  In this study, 109 out of 375 (29.1%) elderly men were identified as cognitive impairment. The median urinary concentrations (creatinine adjusted) of V, Co, Cu, Sr, and Mo in the participants with and without cognitive impairment were 1.31, 0.15, 8.96, 62.15, 73.75 μg·g^-1 and 1.04, 0.12, 7.68, 49.32, 62.60 μg·g^-1, respectively, and the concentrations of V, Co, Cu, and Sr in those with cognitive impairment were higher than those without (all P < 0.05). After confounder adjustment, for each unit increase of lgCu and lgSr, MMSE scores changed by -0.91 (95% CI: -1.76 - -0.07) and -1.56 (95% CI: -2.92 - -0.20), respectively. In the crude logistic regression model, higher urinary concentrations of selected five trace elements were all associated with increased risks of cognitive impairment across tertiles of each trace element's concentrations (all P_trend < 0.05). After adjusting for confounding factors, higher urinary concentrations of V (OR=2.08, 95% CI: 1.15-3.76 for T₃ vs. T₁), Cu (OR=2.04, 95% CI: 1.15-3.63 for T₃ vs. T₁), and Sr (OR=1.94, 95% CI: 1.10-3.43 for T₃ vs. T₁) were still associated with increased risks of cognitive impairment in a dose-response manner. When the five trace elements were included in the logistic regression model simultaneously, the results showed that urinary Cu concentration was positively associated with the risk of cognitive impairment (OR=1.96, 95%CI: 1.07-3.58 for T₃ vs. T₁).

Conclusion  Higher levels of V, Cu, and Sr in urine may be associated with increased risks of cognitive impairment in elderly men in the selected area of Guangxi.