Association between dietary copper intake and respiratory disease mortality

The aim of this study was to explore the association between copper intake from foods and mortality of respiratory disease among US adults. NHANES 1999-2018 data were linked to National Death Index Mortality Data. A multivariable Cox proportional hazard model and sensitivity analysis were adopted. Restricted cubic splines (RCS) were used to evaluate the potential non-linear relationship. During 500,324 person-years of follow-up (median 9.5 years [IQR 5.1-14.3 years]) between 1999 and 2018, we documented 580 respiratory disease deaths. Compared with individuals in the lowest tertile of dietary copper intake (<0.88 mg/d), those in the middle (≥0.88 and <1.34 mg/d) and highest tertile (>1.34 mg/d) had an adjusted hazard ratio (HR) of 0.68 (95% CI, 0.53, 0.88) and 0.62 (0.40, 0.95) for respiratory disease mortality, respectively. RCS analysis revealed an l-shaped association with a threshold at 1.07 mg/d of copper intake. When copper intake was <1.07 mg/d, each incremental increase in intake was associated with a reduced risk of respiratory disease mortality, with an adjusted HR of 0.48 (95% CI, 0.26-0.90, P=.022). However, when copper intake >1.07 mg/d, the risk of respiratory disease mortality showed no significant reduction, with an adjusted HR of 0.98 (95% CI, 0.76-1.27; P=.886) for each incremental increase in intake. In conclusion, in US adults from the NHANES, an l-shaped association between dietary copper intake and respiratory disease mortality was detected, suggesting that maintaining an optimal level of copper intake may be associated with decreased risk of respiratory disease mortality.