Table 3. Association between mammographic density and invasive breast cancer and ductal carcinoma in situ, overall and by menopausal status.

		Mammographic parenchymal composition	Number	Breast cancer	IR per 1000 Women/y	Adjusted HR(95% CI)
Invasive cancer	Overall	25%<	1933840	7119	0.71	1(reference)
		25-50%	1848284	10670	1.18	1.55(1.50,1.59)
		51-75%	1780992	14813	1.72	2.14(2.07,2.21)
		76-100%	802406	8364	2.13	2.59(2.50,2.69)
	Premenopausal	25%<	133834	790	1.07	1(reference)
		25-50%	302196	2029	1.25	1.18(1.09,1.28)
		51-75%	700600	6699	1.86	1.76(1.63,1.90)
		76-100%	495971	5673	2.26	2.16(2.01,2.34)
	Postmenopausal	25%<	1800006	6329	0.68	1(reference)
		25-50%	1546088	8641	1.16	1.60(1.54,1.65)
		51-75%	1080392	8114	1.62	2.16(2.08,2.24)
		76-100%	306435	2691	1.90	2.53(2.40,2.65)
Ductal carcinoma in situ	Overall	25%<	1926721	507	0.05	1(reference)
		25-50%	1837614	876	0.09	1.65(1.47,1.84)
		51-75%	1766179	1317	0.15	2.20(1.97,2.47)
		76-100%	794042	802	0.20	2.62(2.31,2.98)
	Premenopausal	25%<	133044	68	0.09	1(reference)
		25-50%	300167	187	0.11	1.23(0.93,1.63)
		51-75%	693901	678	0.18	1.90(1.48,2.45)
		76-100%	490298	605	0.24	2.31(1.79,2.98)
	Postmenopausal	25%<	1793677	439	0.04	1(reference)
		25-50%	1537447	689	0.09	1.75(1.55,1.98)
		51-75%	1072278	639	0.12	2.24(1.96,2.56)
		76-100%	303744	197	0.13	2.37(1.98,2.84)

Abbreviation: IR – incidence rate, y – year, HR (95% CI) - hazard ratio (95% confidence interval)

Adjusted for age (continuous), height (continuous), BMI (continuous), hormone therapy (never, <2 years, <5 and ≥2 years, ≥5 years, unknown), parity (0, 1, ≥2 births), duration of breast feeding (none, <6 months, <12 and ≥6 months, ≥12 months, unknown), use of oral contraceptives (never, <1 year, ≥1 year, unknown), age at menarche (<14, ≥14 years), alcohol consumption (never drinker, mild to moderate, heavy), smoking status (never, current, or past), regular exercise (binary), and baseline menopausal status.