Association between urinary trace elements levels and depressive symptoms among the older population

Late-life depression is a prevalent public health issue among the elderly. Imbalances in trace elements are increasingly recognized as associated with depression; however, the majority of current research has concentrated on examining the link between blood-based trace elements levels and depressive symptoms. Our objective was to determine if a similar correlation is observed between urinary trace elements levels and depressive symptoms.

We employed stratified, multi-stage random sampling to recruit 400 participants, aged 60 years or older, from a community-based population in a city located in southern China. The Patient Health Questionnaire-9 Items (PHQ-9) was utilized to evaluate depressive symptoms. The concentration of trace elements in urine was detected by inductively coupled plasma mass spectrometry. Multiple logistic regression analysis was conducted to assess the association between urinary trace elements levels and depressive symptoms, as well as the interactions between these levels and potential covariates. The Restricted Cubic Spline (RCS) model with four knots to further explore the association between urinary trace elements and depressive symptoms risk after adjusting for the confounders.

A total of 391 participants were investigated, including 50 (12.6 %) in depressive symptom group and 341 (87.4 %) in non-depressive symptom group. Urinary copper levels were positively correlated with depressive symptoms. Compared with the lowest tertile of urinary copper, the multivariate adjusted odds ratios of depressive symptom were 2.58 (1.18-5.64) in tertile 3. Furthermore, we found the interactions between urinary copper and gender were p < 0.05. The multivariate correction OR for T3 versus T1 in males was 21.10 (1.79-248.13) (P_{for trend} = 0.002). RCS analysis revealed a positive association between copper levels and depressive symptoms (P-overall association = 0.025, and P-nonlinear = 0.161). No significant difference was observed in the risk of developing depressive symptoms among individuals with urinary copper concentrations below 8.22 μg/g creatinine. However, the risk of depressive symptoms increases progressively as the urinary copper concentration exceeds this threshold.

Urinary copper levels are correlated with the development of depressive symptoms, and copper exposure in men is more sensitive to depressive symptoms. Urinary copper, as a non-invasive test, is a promising indicator of depression symptoms in environmental exposure.