Serum Copper-to-Zinc Ratio and Risk of Chronic Obstructive Pulmonary Disease: A Cohort Study

PURPOSE: Serum copper (Cu), zinc (Zn), and Cu/Zn-ratio have emerged as ageing-related biomarkers. We sought to assess the association between Cu/Zn-ratio and chronic obstructive pulmonary disease (COPD) risk. METHODS: Serum Cu and Zn were measured using atomic absorption spectrometry in 2,503 men aged 42–61 years. RESULTS: During a median follow-up of 27.1 years, 210 COPD cases occurred. Serum Cu/Zn-ratio and Cu concentrations were linearly associated with COPD risk, whereas the relationship was curvilinear for Zn and COPD risk. A unit increase in Cu/Zn-ratio was associated with an increased COPD risk in multivariable analysis (hazard ratio, HR 1.81; 95% CI 1.08–3.05). The corresponding adjusted HR (95% CI) was 3.17 (1.40–7.15) for Cu. Compared to the bottom tertile of Zn, the HRs (95% CIs) were 0.68 (0.48–0.97) and 1.01 (0.73–1.41) for the middle and top tertiles of Zn, respectively. CONCLUSIONS: Increased serum Cu/Zn-ratio and Cu concentrations were linearly associated with an increased COPD risk in men.