Table I.

Characteristics of breast cancer cases and controls

	Cases (n = 1509)	Controls (n = 1383)	P value
Age in years
Mean ± SD	48.0 ± 12.0	47.2 ± 17.2	0.08
<50 years, No. (%)	878 (58.4)	799 (57.9)	0.76
Study site, No.
Nigeria	681	282
Barbados	93	244
Baltimore	117	111
Pennsylvania	151	272
Chicago	268	261
Northern California	199	213
Percentage of African ancestry, mean ± SD
Nigerian	98.0 ± 1.2	98.1 ± 1.0	0.08
Barbadian	85.6 ± 10.4	85.7 ± 9.8	0.93
African American	77.6 ± 13.5	78.7 ± 12.0	0.10
Baltimore	80.7 ± 13.3	79.5 ± 12.2
Pennsylvania	78.0 ± 13.4	79.3 ± 11.2
Chicago	77.3 ± 14.1	79.6 ± 11.5
Northern California	75.8 ± 12.5	76.3 ± 13.1