Figure 3.

(A–F) used restricted cubic spline modeling to analyze the relationship between metals, trace minerals, and COPD (ln-transformed). (A,B) is the relationship between copper, selenium, and COPD in all survey subjects, (C,D) is the relationship between copper, selenium, and COPD in males, and (E,F) is the relationship between copper, selenium, and COPD in females. The analysis adjusted for age, smoke, ratio of family income to poverty, BMI, sex, race education, drink, second-hand smoke exposure, serum cotinine, hypertension, and diabetes. The black solid line represents the combined restricted cubic spline curve model, and the shaded part represents the 95% CI of the combined curve.