Table 3.

Association between early life exposures and promoter methylation of E-cadherin, p16, and RAR-β₂ genes in breast tumors among postmenopausal women: case-case comparisons

	E-cadherin			p16			RAR-β2
	M	UM	OR (95% CI) 1	M	UM	OR (95% CI) 1	M	UM	OR (95% CI) 1
Birth weight (kg)
≤2.5	11	57	0.77 (0.38–1.54)	13	55	0.66 (0.34–1.26)	18	50	1.03 (0.57–1.85)
2.6–3.9	82	311	1.0	107	286	1.0	103	290	1.0
>3.9	11	48	0.86 (0.42–1.73)	12	47	0.68 (0.35–1.34)	17	42	1.20 (0.65–2.22)
Birth order
First born	38	173	1.0	41	170	1.0	55	156	1.0
Other than first born	73	278	1.18 (0.76–1.83)	105	246	1.78 (1.17–2.70)	100	251	1.14 (0.77–1.69)
Maternal age at delivery (yrs)
<25	40	181	1.0	49	172	1.0	59	162	1.0
25–30	30	131	1.02 (0.60–1.73)	46	115	1.37 (0.86–2.20)	53	108	1.35 (0.86–2.11)
>30	34	124	1.20 (0.72–2.02)	42	116	1.26 (0.78–2.04)	35	123	0.80 (0.49–1.29)
Having been breastfed
Yes	53	208	1.0	72	189	1.0	64	197	1.0
No	33	140	1.06 (0.64–1.77)	39	134	0.79 (0.49–1.26)	54	119	1.30 (0.83–2.04)
Age at menarche (yrs)
<12	25	103	0.94 (0.56–1.58)	32	96	0.93 (0.58–1.49)	33	95	0.88 (0.55–1.40)
12–13	64	249	1.0	85	228	1.0	89	224	1.0
>13	22	103	0.77 (0.45–1.33)	30	95	0.83 (0.51–1.35)	35	90	1.00 (0.63–1.60)
Age at first live birth (yrs)
<23	49	163	1.0	59	153	1.0	62	150	1.0
23–29	31	169	0.56 (0.33–0.95)	49	151	0.89 (0.56–1.42)	58	142	1.00 (0.64–1.56)
≥30	8	44	0.56 (0.24–1.28)	8	44	0.51 (0.22–1.16)	14	38	0.90 (0.45–1.81)
Adult height (m)
<1.60	40	156	1.02	49	147	1.02	60	136	1.02
1.60–1.64	32	152	0.94 (0.55–1.61)	50	134	1.18 (0.73–1.91)	48	136	0.78 (0.49–1.26)
≥1.65	39	147	1.24 (0.71–2.18)	48	138	1.17 (0.70–1.98)	49	137	0.71 (0.43–1.17)
Weight at 20 years (kg)
<54.4	53	219	1.0	70	202	1.0	76	196	1.0
≥54.4	58	236	1.04 (0.68–1.58)	77	217	1.08 (0.74–1.58)	81	213	0.97 (0.67–1.41)

M – methylated; UM – un-methylated

¹Odds ratios and 95% confidence intervals adjusted for age, race, education, and ER status.

²Odds ratios and 95% confidence intervals adjusted for age, race, education, ER status, weight at 20s, weight 2 years ago, and maternal height.