Infertility and risk of breast cancer in men: a national case–control study in England and Wales

Table 4 Risk of breast cancer in men in relation to age at birth of first biological child

Age at birth of first child (years)	Cases No. %		Controls No. %		Odds ratio^a (95% CI) All subjects	P	Odds ratio^a (95% CI) excluding potentially confounding conditions^b	P
No children	383	19.2	174	10.9	1.00		1.00
< 20	65	3.3	30	1.9	1.14 (0.70–1.88)	0.60	1.33 (0.79–2.24)	0.28
20–4	426	21.3	300	18.8	0.79 (0.61–1.01)	0.06	0.82 (0.63–1.07)	0.15
25–9	588	29.4	614	38.4	0.57 (0.45–0.72)	< 0.001	0.60 (0.47–0.77)	< 0.001
30–4	317	15.9	344	21.5	0.56 (0.43–0.72)	< 0.001	0.59 (0.45–0.78)	< 0.001
≥ 35	169	8.5	117	7.3	0.84 (0.61–1.16)	0.30	0.88 (0.63–1.23)	0.47
Age not known	50	2.5	18	1.1	1.48 (0.80–2.71)	0.21	1.71 (0.88–3.30)	0.11
Linear trend per 5 years of age^c					0.97 (0.91–1.04)	0.38	0.96 (0.89–1.03)	0.27
Total	1998	100.0	1597	100.0

CI, confidence interval
^aAdjusted for age, socio-economic status (Acorn score [20]), year of interview, marital status and geographical region of residence
^bExcluding 11 men with Klinefelter syndrome, 9 with potentially confounding prior cancers, 29 who were severely obese at age 20 (2) or at age 40 (27), and 169 with testicular diseases
^c Excluding no children category