Table 1. Standardised incidence ratios (SIRs) of breast cancer by age.

		Age at baseline
Variables	Total	25−	30−	35−	40−	45−	50−	55−	60−	65−	70−	75−	80−	85+
Frequency	1492	171	152	176	214	167	144	108	86	63	76	56	44	35
Person-years	9109	738	794	1032	1215	1183	1003	737	579	467	438	364	291	268
New breast cancers Observed (N)	65	2	4	5	6	6	10	7	5	6	7	4	1	2
New breast cancers expected (N)	16.49	0.05	0.16	0.53	1.23	2.06	2.17	1.85	1.64	1.60	1.61	1.45	1.15	0.99
Rate per 105 observed	713.6	271.0	503.8	484.5	493.8	507.2	997.0	949.8	863.6	1284.8	1598.2	1098.9	343.6	746.3
Rate per 105 expected	181.0	6.8	20.8	51.5	101.4	173.9	216.6	250.8	284	342.7	366.9	397.6	393.7	369.1
SIR	3.9	40.1	30.3	9.4	5	2.9	4.1	3.8	3.1	3.8	5	2.8	0.9	2.1
95% CI	3.1–5.0	11.0–146	7.8–51	4.3–23.4	2.3–10.9	1.3–6.2	2.5–8.4	1.9–8.0	1.3–7.3	1.7–8.2	2.1–9.0	1.1–7.3	0.2–5.1	0.6–7.3
P-value	<0.0001	0.02	0.002	0.002	0.007	0.05	0.0008	0.009	0.05	0.02	0.006	0.10	0.92	0.41