Table 2.

The hazard ratio for breast cancer according to zinc level (tertiles).

Variables	Breast Cases/ Total	Univariate HR (95% CI) P	Multivariate * HR (95% CI) P
Zinc µg/L
≤5797	38/329	1	1
5797–6433	51/329	1.38 (0.91–2.10) 0.13	1.39 (0.90–2.12) 0.13
>6433	34/331	0.90 (0.57–1.44) 0.67	0.91 (0.57–1.47) 0.70
Total	123/989
Zinc
<5797	38/329	1	1
>5797	85/660	1.14 (0.78–1.67) 0.51	1.15 (0.78–1.70) 0.48
Year of birth
≤1965	38/239	1	1
January 1965–1975	28/224	0.79 (0.49–1.29) 0.35	0.61 (0.26–1.41) 0.25
January 1975–1985	43/337	0.85 (0.55–1.31) 0.45	0.66 (0.20–2.16) 0.49
1985	14/189	0.58 (0.31–1.07) 0.08	0.40 (0.11–1.44) 0.16
Age at blood draw (years).
≤40	62/566	1	1
40.01–50	30/216	1.22 (0.79–1.90) 0.36	1.55 (0.65–3.73) 0.32
>50	31/207	1.28 (0.83–1.79) 0.26	1.18 (0.36–3.90) 0.78
Oophorectomy
No	30/413	1	1
Yes (time-dependent)	93/576	0.87 (0.61–1.26) 0.46	0.64 (0.39–1.03) 0.07
Oral contraceptive use
No	59/502	1	1
Yes	64/481	1.10 (0.78–1.57) 0.58	1.22 (0.83–1.78) 0.32
HRT
No	91/720	1	1
Yes	32/263	0.82 (0.55–1.23) 0.34	0.78 (0.50–1.78) 0.32
Smoking
No	59/553	1	1
Current	35/222	1.52 (1.00–2.31) 0.05	1.51 (0.99–2.30) 0.06
Former	29/209	1.30 (0.83–2.03) 0.25	1.22 (0.78–1.92) 0.38
BMI at blood taken
≤median (23.05)	63/464	1	1
>median (23.05)	57/477	0.84 (0.59–1.21) 0.35	0.77 (0.53–1.14) 0.19
Missing	3/48

* Adjusted by all the variables listed in the left column.