<p>Toxic metal mixtures are associated with cognitive function and related health outcomes in elderly people. However, the combined effects of toxic metal exposure and sleep difficulties on cognitive function in this population remain unclear. This research aimed to investigate whether exposure to a mixture of toxic metals—cadmium (Cd), arsenic (As), lead (Pb), thallium (Tl), and molybdenum (Mo)—affects cognitive abilities and to analyze whether sleep difficulties alter these effects. There were 1262 elderly Chinese enrolled in the study, and metal concentrations in whole blood were collected by inductively coupled plasma mass spectrometry (ICP-MS). Cognitive decline was evaluated by the Mini-Mental State Examination (MMSE). Sleep difficulties were assessed using the Pittsburgh Sleep Quality Index (PSQI) scale. To explore the association between the mixtures of toxic metals and cognitive decline, Bayesian kernel machine regression (BKMR) and weighted quantile sum regression (WQS) models were utilized, while linear regression was used to examine whether sleep difficulties increased the impact of toxic metals on MMSE scores. The results of the study indicate that the concentration of toxic metal mixtures is negatively correlated with cognitive function. And an interaction was observed where the negative association between Cd and MMSE scores was stronger among individuals with sleep difficulties. Further studies are needed to confirm the mechanisms linking sleep difficulties, toxic metals, and cognitive decline in elderly people.</p>