Table 5.

Threshold effect analysis of iron, zinc and copper on the prevalence of total CVD risk using piecewise binary logistic regression models.

	Inflection point	group	Mean difference (95% CI)	P- value	P for log likelihood ratio test
Iron (mg)	7.71	≤7.71	0.83 (0.71–0.97)	0.018	0.221
		>7.71	0.90 (0.84–0.97)	0.007
Zinc (mg)	6.61	≤6.61	0.75 (0.66–0.86)	<0.001	0.019
		>6.61	0.90 (0.83–0.98)	0.012
Copper (mg)	0.74	≤0.74	0.71 (0.61–0.83)	<0.001	0.025
		>0.74	0.86 (0.80–0.94)	<0.001

OR, Odd ratio; CI, confidence interval.

Iron, zinc and copper were log 2 transformed for fitting the piecewise binary logistic regression model.

Analyses was adjusted for age, sex, race, education levels, poverty, smoking, drinking, BMI, total cholesterol, dietary supplement use, diabetes and hypertension.