Table 2.

Association between serum zinc and knee chondrocalcinosis (n = 12,362)

	Tertiles of serum zinc (μmol/L)			P for trend
	1 (≤ 12.1)	2 (12.2–14.2)	3 (≥ 14.3)
Total
Knee chondrocalcinosis (%)	1.7	1.2	0.8	–
N for kneea	8354	8285	8082	–
Model 1 (95% CI)	1.00 (reference)	0.74 (0.50, 1.09)	0.56 (0.36, 0.86)	0.009
Model 2 (95% CI)	1.00 (reference)	0.77 (0.52, 1.14)	0.59 (0.38, 0.91)	0.018
Model 3 (95% CI)	1.00 (reference)	0.73 (0.49, 1.08)	0.54 (0.35, 0.84)	0.006
Model 4 (95% CI)	1.00 (reference)	0.75 (0.51, 1.12)	0.56 (0.37, 0.87)	0.010
Model 5 (95% CI)	1.00 (reference)	0.75 (0.51, 1.11)	0.58 (0.37, 0.88)	0.012
Model 6 (95% CI)	1.00 (reference)	0.75 (0.50, 1.11)	0.56 (0.37, 0.87)	0.011

Model 1 included age (40–49, 50–59, 60–69, ≥ 70 years), body mass index (< 28, ≥ 28 kg/m²) and sex (n = 12,362);

Model 2 added serum iron (tertiles) on the basis of model 1 (n = 12,357);

Model 3 added serum calcium (tertiles) on the basis of model 1 (n = 12,264);

Model 4 added serum magnesium (tertiles) on the basis of model 1 (n = 12,362);

Model 5 added serum copper (tertiles) on the basis of model 1 (n = 12,362);

Model 6 added serum phosphorus (tertiles) on the basis of model 1 (n = 12,264)

^aThree right knees with K-L 4 grade were excluded for analysis (data from the contralateral knees were retained)

N number, CI confidence interval