Association of copper exposure with metabolic syndrome: a dose-response meta-analysis

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Metabolic syndrome (MetS) represents a cluster of interconnected metabolic derangements with a growing global prevalence. The association of copper (Cu) exposure with the odds of MetS remains unclear. This dose-response meta-analysis aimed to examine the relationship between urinary and serum Cu concentrations and MetS. We searched Cochrane library, Web of Science, PubMed, and Scopus from inception to 4 February 2026. Studies providing association estimates for the relationship between serum or urinary Cu and MetS were included. Pooled effect sizes were presented as odds ratios (ORs) with 95% confidence intervals (CIs), calculated with the use of random-effects models. Twenty-three studies with 69,121 participants and 9,964 MetS cases were included. Higher serum Cu concentrations were significantly linked to elevated odds of MetS (OR = 1.17, 95% CI = 1.02–1.35), with considerable heterogeneity (I² = 79.6%, P < 0.001). Dose-response analysis revealed no significant linear association; however, a significant non-linear relationship was identified, with the odds of MetS increasing more markedly at serum Cu concentrations above approximately 1,100 µg/L ( P = 0.047). Higher urinary Cu concentrations were also significantly associated with greater odds of MetS (OR = 1.41, 95% CI: 1.03–1.95; I² = 83.1%). The associations for both serum and urinary Cu were attenuated after adjustment for lifestyle-related factors and BMI. Elevated serum and urinary Cu concentrations were significantly linked to an elevated odds of MetS, with evidence of a non-linear dose-response association. Lifestyle factors may confound this association. Not applicable.