Table 3. ERR estimates for breast cancer incidence and mortality by birth cohort, US Radiologic Technologists study, 1983–2008.

Year of birth	ERR at 100 mGya	95% CI	P-value	Fitted excess cases	Observed cases	Mean dose (mGy)
Incidence
Before 1930	0.16	0.03, 0.39	0.01	44.2	216	167
1930–1939	−0.1	<−0.3, 0.11	0.41	−21	406	49
1940–1949	−0.14	<−0.5, 0.22	0.4	−25.8	745	25
1950+	−0.25	<−0.5, 0.31	0.27	−27.9	555	14
		Phet=0.08
Common ERR	0.07	−0.005, 0.19	0.09	54.3	1922	30
Mortality
Before 1930	0.26	0.08, 0.63	<0.001	43.7	128	217
1930–1939	0.28	−0.08, 0.89	0.26	19.5	159	51
1940–1949	1.61	0.20, 4.50	0.01	52.6	190	25
1950+	0.61	<−0.5, 4.70	>0.5	8.6	109	14
		Phet=0.35
Common ERR	0.31	0.11, 0.67	<0.001	88.5	586	37

Abbreviations: BMI=body mass index; CI=confidence interval; ERR=excess relative risk; Phet=P-value of test for hetergeneity over birth cohorts.

^aAdjusted for attained age, birth cohort category, menopause status, family history of breast cancer, baseline BMI and use of hormone replacement therapy.