Table 4.

Distributions of selected basal-like risk factors among controls according to race and menopausal status

Characteristica	African-American premenopausal (%)	African-American postmenopausal (%)	White premenopausal (%)	White postmenopausal (%)
Age at menarche <13 Pb =0.03	54	36	45	46
Never breastfed P = 0.0001	76	66	61	61
Lifetime duration breastfeeding ≥4 months P < 0.0001	13	27	29	21
Parous women ≥2 children breastfed P < 0.0001	13	24	33	19
≥4 months breastfeeding per child P < 0.0001	10	18	34	12

^aPercentages in table are adjusted for sampling probabilities

^bChi square test adjusted for sampling probabilities