Circulating serum xenoestrogens and mammographic breast density

Breast Cancer Research

Table 1 Characteristics of study participants (N = 264), Wisconsin Breast Density Study, 2008 to 2009

	Mean ± SD or n(%)
Age (years)	60.6 ± 4.4
Body mass index (kg/m²)^a	28.9 ± 6.6
First-degree family history of breast cancer	63 (23.9)
Nulliparous	67 (25.4)
Smoking status Never Former Current	159 (60.2) 91 (34.5) 14 (13.3)
Vigorous physical activity (hours per week)^b	4.2 ± 5.0
College degree^c	153 (58.2)

SD, standard deviation. ^aBody mass index data was missing for two subjects. ^bPhysically vigorous activities that cause large increases in heart rate or breathing, such as sports activities, climbing stairs, heavy gardening, or lifting/carrying heavy objects. ^cEducation data were missing for one subject.

ISSN: 1465-542X