Table 2. Breast cancer risk according to relationship to AT patient.

Relationship to AT patient	No.	PY	Obs	Exp	SIR	95% CI
Mother	37	1559.5	3	0.42	7.14	1.44–20.9
All relatives except mother	670	31 167.4	25	18.53	1.35	0.87–1.99
Aunt	99	4033.6	2	1.26	1.59	0.18–5.73
Grandmother	65	4291.6	6	3.24	1.85	0.68–4.03
Grandaunt	158	9962.8	9	7.59	1.19	0.54–2.25
Great-grandmother	85	6374.2	5	5.34	0.94	0.30–2.19
Sister	28	475.9	0	0.03	—
Cousin	116	2032.7	0	0.12	—
Daughter of great-aunt or -uncle	81	2712.9	3	0.45	6.67	1.34–19.5
Other relationshipa	38	1283.6	0	0.59	—

^aFor example, great great grandmother, nephew.