Table 4 Risk estimates for mammographic density in studies using percentage mammographic density as a measure.

Country	Year	Age	Cases (n)	Controls (n)	Comparison	OR (95 % CI)	Reference
CI: confidence intervals; OR: odds ratio.
USA	1991	35–74	266	301	< 5 % vs. ≥ 65 %	4.3 (2.1–8.8)	123
USA	1995	35–75	1 880	2 152	0 % vs. ≥ 75 %	4.3 (3.1–6.1)	124
Canada	1995	40–59	330	330	0 % vs. ≥ 75 %	6.0 (2.8–13.0)	42
Netherlands	2000	> 45	129	517	< 5 % vs. > 25 %	2.9 (1.6–5.6)	125
USA	2002	< 50	547	472	upper vs. lower quartile	4.4 (3.0–6.7)	126
UK	2005	40–80	111	3 100	0.5 % vs. > 46 %	3.5 (1.4–5.2)	127
Japan	2005	premenopausal	71	370	0 % vs. 75–100 %	4.37 (1.24–15.4)	128
Japan	2005	postmenopausal	75	389	0 % vs. 75–100 %	4.19 (1.33–13.2)	128
USA	2006	60	607	667	< 10 % vs. > 50 %	3.6 (2.3–5.6)	129
Canada	2007	40–70	1 114	1 114	< 10 % vs. ≥ 75 %	4.7 (3.0–7.4)	39
Japan	2008	50–93	205	223	highest vs. lowest quintile	3.02 (1.58–5.77)	130
Germany	2011	28–80	1 025	520	< 10 % vs. ≥ 50 %	2.7 (1.3–5.4)	38
Singapore	2011	45–69	491	982	< 10 % vs. > 75 %	5.54 (2.38–12.9)	131