Independent and Combined Associations of Urinary Heavy Metal Exposures with Serum α-Klotho in Middle-Aged and Older Adults

α-Klotho is an anti-aging protein linked to various age-related diseases. Environmental metal exposure has been associated with oxidative stress and aging, but its effect on α-Klotho levels remains unclear. This study investigated the relationship between urinary metal concentrations and serum α-Klotho levels using data from the National Health and Nutrition Examination Survey (NHANES) 2007-2016 cycles. A total of 4071 adults aged 40 to 79 years were included in the analysis. After adjusting for potential confounders, positive associations were found between serum α-Klotho levels and barium (Ba), cesium (Cs), and molybdenum (Mo), while tungsten (W) and uranium (U) were negatively correlated with α-Klotho levels. The combined effects of multiple metals were further analyzed using the qgcomp model, which demonstrated a negative correlation between increased metal mixtures and serum α-Klotho levels. Specifically, U, total arsenic (t-As), W, cadmium (Cd), antimony (Sb), and lead (Pb) contributed to the reduction of α-Klotho levels, while Ba, Cs, dimethylarsinic acid (DMA), Mo, thallium (Tl), and cobalt (Co) were positively associated with α-Klotho levels. These findings suggest that exposure to certain metals, particularly in combination, may reduce serum α-Klotho levels, potentially accelerating aging processes. Further studies should investigate the underlying mechanisms responsible for these associations.