Table II.

Frequency of dairy intake and risk of breast cancer in different subgroups.

	Dairy intake, days/week
Subjects	<1	1–2	3–4	5–7	Trend P-value
Total
Controls	332	432	405	292
Cases	391	434	296	165
OR (95% CI)a	1b	0.91 (0.72–1.16)	0.69 (0.53–0.90)	0.53 (0.39–0.72)	<0.001
Residence
Rural
Cases	223	225	121	48
OR (95% CI)a	1b	1.13 (0.81–1.59)	0.86 (0.58–1.28)	0.67 (0.39–1.16)	0.138
Urban
Cases	151	189	157	107
OR (95% CI)a	1b	0.74 (0.52–1.06)	0.56 (0.39–0.81)	0.45 (0.30–0.66)	<0.001
Age, years
25–44
Cases	133	166	113	55
OR (95% CI)a	1b	1.03 (0.69–1.53)	0.73 (0.48–1.12)	0.66 (0.40–1.10)	0.043
45–59
Cases	229	226	153	92
OR (95% CI)a	1b	0.82 (0.59–1.13)	0.67 (0.46–0.97)	0.39 (0.26–0.60)	<0.001
60–70
Cases	29	42	30	18
OR (95% CI)a	1b	1.27 (0.47–3.43)	0.89 (0.31–2.50)	1.12 (0.32–3.89)	0.900
Education
Junior high school or lower
Cases	260	230	127	52
OR (95% CI)a	1b	1.07 (0.78–1.47)	0.83 (0.57–1.20)	0.69 (0.43–1.13)	0.106
Senior high school or above
Cases	124	195	154	105
OR (95% CI)a	1b	0.70 (0.48–1.03)	0.51 (0.34–0.76)	0.39 (0.25–0.59)	<0.001

^aAdjusted for residence (urban, rural), age (25–44, 45–59, 60–70 years), education (junior high school or lower, senior high school or above), family monthly income (<5,000, ≥50,00 RMB), body mass index (<24.0, ≥24.0 kg/m²), age of menarche (≤12, 13–14, 15–16, ≥17 years), number of births (0, 1, 2, ≥3), age at first childbirth (<20, 20–24, 25–29, 30–35, ≥35 years), breast-feeding (no, yes), menopausal status (premenopausal, postmenopausal), family history of breast cancer in first degree relatives (no, yes), cigarette smoking (never, sometimes, often), alcohol drinking (never, sometimes, often) and physical activity (never, sometimes, often). For the stratified analyses, the stratification variable was excluded from the model.

^bReference for calculating OR. OR, odds ratio; CI, confidence interval.