Table 2.

The Age-adjusted Association Between Alcohol Drinking and the Risk of Developing Asynchronous Contralateral Breast Cancer, the Women's Environmental Cancer and Radiation Epidemiology Study, 1985–2001

	Breast Cancer				Rate Ratioa	95% Confidence Interval
	Unilateral		Asynchronous Contralateral
	No.	%b	No.	%
Ever drank regularly
No	550	42.4	275	39.0	1.0
Yes	846	57.6	431	61.0	1.3	1.0, 1.6
Ever drank regularly during at-risk periodc
No	672	52.0	348	49.3	1.0
Yes	722	48.0	358	50.7	1.2	0.9, 1.5
Lifetime duration of drinking
Never	550	42.4	275	39.2	1.0
<20 years	279	19.4	137	19.5	1.2	0.9, 1.7
20–<30 years	286	19.3	143	20.4	1.3	0.9, 1.7
≥30 years	276	18.9	147	20.9	1.4	1.0, 1.9
Ptrendd					0.03
Average drinking amount
Never	550	43.1	275	39.5	1.0
<1 drink/day	659	45.2	338	48.5	1.3	1.0, 1.7
≥1 drink/day	171	11.7	84	12.1	1.2	0.8, 1.7
Ptrendd					0.16
Starting age
Never	550	42.4	275	39.0	1.0
≥20 years of age	526	34.5	282	40.0	1.4	1.1, 1.8
<20 years of age	315	23.1	148	21.0	1.1	0.8, 1.5

^aAccounting for countermatching and adjusted for age at first diagnosis.

^bProportions are weighted for the countermatching.

^cConsumption during the at-risk period was defined as starting prior to or during the period between the first diagnosis and the reference date and stopping during or after the period between the first diagnosis and the reference date.

^dTest for trend across categories.