. 2016 Mar 4;124(7):1042–1049. doi: 10.1289/ehp.1510334

Table 2.

Waterborne ingested nitrate from 18 years of age to 2 years before study interview and breast cancer associations by menopausal status. Odds ratios (ORs) and 95% confidence intervals (CIs).

Menopausal status	Cases (n)	Controls (n)	OR^a (95% CI)	OR^b (95% CI)	Cases^c (n)	Controls^c (n)	OR^b (95% CI)
Postmenopausal	913	1,173			888	1,080
< 2.3 mg/day	227	294	Reference	Reference	222	289	Reference
≥ 2.3–4.0 mg/day	232	293	1.06 (0.82, 1.36)	1.09 (0.84, 1.41)	229	285	1.11 (0.86, 1.45)
> 4.0–8.8 mg/day	222	293	1.08 (0.82, 1.41)	1.07 (0.81, 1.42)	213	263	1.10 (0.83, 1.46)
> 8.8 mg/day	232	293	1.28 (0.92, 1.77)	1.29 (0.92, 1.81)	224	243	1.32 (0.93, 1.86)
p for trend			0.19	0.20			0.16
Premenopausal	332	347			330	339
< 1.8 mg/day	72	87	Reference	Reference^d	72	86	Reference^d
≥ 1.8–3.1 mg/day	87	87	1.24 (0.79, 1.92)	1.31 (0.83, 2.06)	86	86	1.28 (0.81, 2.02)
> 3.1–6.3 mg/day	85	87	1.08 (0.68, 1.72)	1.03 (0.64, 1.66)	85	85	0.99 (0.61, 1.60)
> 6.3 mg/day	88	86	1.11 (0.66, 1.86)	1.14 (0.67, 1.94)	87	82	1.05 (0.61, 1.80)
p for trend			0.78	0.80			0.97
Pre + Postmenopausal	1,245	1,520			1,218	1,419
< 2.2 mg/day	319	380	Reference	Reference	315	374	Reference
≥ 2.2–3.8 mg/day	303	380	0.96 (0.77, 1.19)	0.98 (0.79, 1.23)	298	373	0.98 (0.78, 1.22)
> 3.8–8.1 mg/day	316	380	1.04 (0.83, 1.31)	1.01 (0.80, 1.28)	308	351	1.01 (0.80, 1.28)
> 8.1 mg/day	307	380	1.09 (0.83, 1.43)	1.08 (0.82, 1.43)	297	321	1.08 (0.81, 1.44)
p for trend			0.53	0.64			0.63
Trend p-values were derived from a likelihood ratio test that compared a model including the categorical nitrate intake variable as an ordinal variable (0, 1, 2) with a model that excluded this variable. ^aAdjusted for study area, age, and education. ^bAdjusted for study area, age, education, body mass index, family history of breast cancer, age at first birth, age at menopause, use of oral contraceptives, and energy intake. ^cWomen with unreliable interviews or missing data on interview quality (postmenopausal, n = 118; premenopausal, n = 10) were excluded. ^dAge at menopause was excluded from the adjustment for premenopausal women.