Table 1. Risk of breast cancer according to number of prescriptions for antibiotics.

	Cases		Controls
No. of prescriptions	No.	%	No.	%	OR	95% CI
0	489	17.9	5047	18.5	1 (reference)	—
1–5	1327	48.6	13 078	47.9	1.02	0.91–1.14
6–10	467	17.1	4859	17.8	0.94	0.82–1.08
>10	445	16.3	4296	15.7	1.00	0.86–1.15
Wald test for homogeneity P=0.35