Table 2. Odds ratios for risk of death from breast cancer by screening history 1995–2004.

Screening factors	No. of cases/controls	Odds ratio (95% CI)
Ever attended
Never	77/63	1
Ever	207/505	0.35 (0.24, 0.50)
Self-selection corrected (invitation effect)		0.65 (0.48, 0.88)
Self-selection corrected (screening effect)		0.52 (0.32, 0.84)
Number of screens attended
1	86/185	1
2	66/198	0.70 (0.43, 1.11)
3+	55/122	1.03 (0.59, 1.77)
None	77/63	2.51 (1.56, 4.03)
Time since last screen
<1 year	65/113	1
1<2 years	41/121	0.43 (0.24, 0.77)
2<4 years	62/175	0.48 (0.28, 0.81)
4+ years	39/96	0.55 (0.29, 1.04)
Never screened	77/63	1.71 (1.03, 2.80)
Age at first screen (screened women only)
<52	53/144	1
52–53	50/91	2.38 (1.02, 5.57)
54<58	60/137	2.25 (0.83, 6.09)
>58	44/133	1.54 (0.33, 7.01)