Table 1.

Characteristics of breast cancer cases versus cancer-free females with SLE

	Breast cancer cases in SLE(n = 86)	Cancer-free women with SLE (n = 4,498)
Mean age at cohort entry (years)	43.1 (40.6, 45.5)*	38.1 (37.7, 38.5)
White (%)	81.4 (71.6, 89)	62.4 (61, 63.9)
Disease duration at entry (years)	5.1 (3.3, 6.8)	6.0 (5.8, 6.2)
Positive dsDNA antibody at entry (%)	26.3 (17, 37.3)	27.1 (25.8, 28.4)
Activity top quartile at entry (%)**	30.6 (19.6, 43.7)	40.8 (39.3, 42.3)
Number of pregnancies	1.42 (1.16, 1.72)	1.34 (1.31, 1.38)
Menopause (%)	65.2 (52.4, 76.5)	36.6 (35, 38.2)
Family history of breast cancer (%)	23.5 (10.7, 41.2)	11 (9.5, 12.8)

^*95% confidence interval

^**Assessed by Systemic Lupus Erythematosus Disease Activity Index-2K scores; at one centre (San Francisco), disease activity was captured only with self-report items.