Serum Cu/Zn ratio is significantly associated with long COVID

Since the coronavirus disease 2019 (COVID-19) pandemic, many people have been affected by COVID-19. However, at present, neither reliable predictors of long COVID nor effective treatments are widely established. The aim of this observational study was to clarify whether Zn and Cu concentrations or the ratio of Cu to Zn were associated with the severity of COVID-19 or long COVID. Zn and Cu concentrations in serum samples from COVID-19 patients over time were measured and their associations with COVID-19-related clinical symptoms were assessed using logistic regression analyses. Data from a total of 77 patients were analyzed. For 52 patients whose blood samples were collected at the time of the first medical examination, a low Zn level and an elevated ratio of Cu to Zn were significantly correlated with the severity of COVID-19 (Odds ratio [OR] 0.476, 95% confidence interval [CI] 0.230 to 0.985, P = 0.045 for Zn; OR 2.752, 95% CI 1.251 to 6.052, P = 0.012 for Cu/Zn, respectively). For the 38 patients whose blood samples were collected at 3–10 weeks after symptom onset, a low ratio of Cu to Zn was significantly correlated with long COVID (OR 0.125, 95% CI 0.022 to 0.709, P = 0.019). The ratio of Cu to Zn at 3–10 weeks after symptom onset was significantly associated with long COVID.