Table 3.

Relative risk [HR (95% CI)] of breast cancer according to days of use of tetracyclines and macrolides, excluding or not excluding the other drug group

Antibiotic1-10 d11-30 d31-100 d101+ dTrend*
Tetracyclines1.04 (0.98-1.10)1.04 (0.97-1.11)1.13 (1.04-1.22)1.23 (1.11-1.36)1.06 (1.02-1.09)
Tetracyclines excluding macrolides1.06 (0.98-1.15)1.08 (0.99-1.18)1.16 (1.04-1.30)1.14 (0.99-1.31)1.04 (0.99-1.09)
Macrolides1.05 (1.01-1.10)1.06 (1.01-1.11)1.03 (0.95-1.11)1.16 (0.98-1.36)1.01 (0.97-1.04)
Macrolides excluding tetracyclines1.07 (1.03-1.12)1.03 (0.96-1.09)1.01 (0.91-1.12)1.18 (0.93-1.49)0.98 (0.94-1.03)
  • NOTE: Reference group was not used; controlled for hormone use.

  • * Relative risk per increase in one duration category; nonusers were excluded.