Table 3

Relation of cimetidine use to risk of breast cancer among female users of H2 blockers in GHC, 1984–1996

Controls (N = 4740)Cases (N = 474)RR (95% CI)
N%N%
Ever used cimetidine
No79316.78217.31.0
Yes394783.339282.71.0 (0.7–1.2)
No. of prescriptions
Never used79316.78217.31.0
 176316.17515.80.9 (0.7–1.3)
 2–387418.49219.41.0 (0.7–1.4)
 4–10114624.211023.20.9 (0.7–1.3)
11–2059012.45311.20.9 (0.6–1.2)
21+57412.16213.11.0 (0.7–1.5)
Time since first eligible prescription
Never used79316.78217.31.0
<2 yr95320.18818.60.9 (0.6–1.2)
2 to <5 yr113423.910923.00.9 (0.7–1.2
5 to <8 yr90619.19119.21.0 (0.7–1.3)
8+ yr95420.110421.91.1 (0.8–1.4)
Time since last prescription
Never used79316.78217.31.0
≤1 yr180438.118238.41.0 (0.7–1.3)
>1 yr to <2 yr49410.4479.90.9 (0.6–1.3)
2 to <5 yr94119.88217.30.8 (0.6–1.2)
5+ yr70814.98117.11.1 (0.8–1.5)