Common genetic variation in IGF1, IGFBP-1, and IGFBP-3 in relation to mammographic density: a cross-sectional study

Table 2 Common insulin-like growth factor (IGF) haplotypes^a and percentage mammographic density, Nurses' Health Study

Block 1 (p = 0.03)^b			Block 2 (p = 0.95)^b			Block 3 (p = 0.009)^b			Block 4 (p = 0.007)^b
Haplotype	Frequency (percentage)	β^c (95% CI)	Haplotype	Frequency (percentage)	β^c (95% CI)	Haplotype	Frequency (percentage)	β^c (95% CI)	Haplotype	Frequency (percentage)	β^c (95% CI)
1A (TG)	82.9	0.16	2A (GCC)	55.0	-0.002	3A (AGGCC)	46.5	0.08	4A (GGAA)	42.4	0.09
		(-0.04 to 0.35)			(-0.15 to 0.14)			(-0.07 to 0.22)			(-0.06 to 0.23)
1B (TA)	13.3	-0.29	2B (GCG)	22.6	-0.04	3B (AGGCG)	13.6	0.03	4B (ACGA)	14.3	-0.03
		(-0.52 to -0.07) ^d			(-0.21 to 0.14)			(-0.18 to 0.24)			(0.24 to 0.19)
Rare	3.9	--	2C (AAC)	12.7	0.03	3C (AGTCC)	11.0	0.15	4C (GGGA)	14.5	0.19
					(-0.17 to 0.24)			(-0.09 to 0.38)			(-0.02 to 0.41)
			2D (ACC)	9.0	0.03	3D (GGGGC)	9.1	-0.39	4D (ACGG)	8.8	-0.34
					(-0.23 to 0.29)			(-0.65 to -0.14) ^e			(-0.61 to -0.06) ^h
			Rare	0.8	--	3E (GGGCC)	8.2	0.35	4E (GGGG)	8.1	0.28
								(0.07 to 0.62) ^f			(0.0007 to 0.55) ⁱ
						3F (GAGGC)	7.6	-0.38	4F (AGAA)	7.6	-0.45
								(-0.65 to -0.12) ^g			(-0.73 to -0.16) ^j
						Rare	4.0	--	Rare	4.3	--

CI, confidence interval. ^aIGF1 haplotype blocks are based on SNPs defined in Table 1. Block 1, SNPs 1 and 2; block 2, SNPs 3 to 5; block 3, SNPs 6 to 10; block 4, SNPs 11 to 14. ^bGlobal test of association based on F statistic comparing model with haplotypes in block and covariates with covariates only. ^cβ coefficients from models that used square-root-transformed mammographic density as the dependent variable. Multivariate-adjusted models including age (continuous), body mass index (continuous), alcohol consumption (category), age at first birth/parity, history of benign breast disease (yes/no), family history of breast cancer (yes/no), menopausal status/postmenopausal hormone use (premenopausal, postmenopausal never user, postmenopausal current user, postmenopausal past user). Results in bold show significant differences: ^d p = 0.009; ^e p = 0.003; ^f p = 0.02; ^g p = 0.005; ^h p = 0.02; ⁱ p = 0.05; ^j p = 0.002.

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