Table 2.

Characteristics of the study participants: analytic sample of the current study (N = 451)

	Mean	SD	Median	Number	%
Age at mammogram, years	48.6	2.6	48.7
BMI, kg/m2	25.9	5.9	24.4
<25				251	56
25–30				111	25
>30				89	20
Percentage mammographic density	43.6	19.5	44.7
Age at first full-term birth	28.1	5.5	28.0
Ethnicity
African American				26	6
White				219	49
Chinese				109	24
Japanese				97	22
Study site
Oakland				184	41
Los Angeles				169	37
Pittsburgh				98	22
Smoking currently				31	7
Menopausal status at time of mammogram
Early perimenopausal				332	74
Premenopausal				118	26
Parity
0				77	17
1				76	17
2				196	43
3				76	17
4				19	4
≥ 5				7	2

Baseline menopause stage information was missing for one participant whose baseline mammogram was chosen; the participant was early perimenopausal at the subsequent (first annual) visit.