Table 2.

Level of aerobic versus anti-anaerobic antibiotic use and risk of colorectal cancer

Author	Outcome	Level of exposure	Anti-anaerobic agents, ES (95% CI)	Anti-aerobic agents, ES (95% CI)
Zhang28	Colon	0 days	Reference	Reference
Zhang28	Colon	1–15 days	1.07 (1.03 to 1.12)	1.00 (0.96 to 1.05)
Zhang28	Colon	16–30 days	1.10 (1.04 to 1.16)	1.11 (1.03 to 1.20)
Zhang28	Colon	31–60 days	1.12 (1.06 to 1.19)	1.00 (0.90 to 1.12)
Zhang28	Colon	>60 days	1.14 (1.07 to 1.21)	0.97 (0.86 to 1.10)
Zhang28	Rectal	0 days	Reference	Reference
Zhang28	Rectal	1–15 days	1.01 (0.95 to 1.07)	0.96 (0.90 to 1.03)
Zhang28	Rectal	16–30 days	0.96 (0.89 to 1.04)	0.92 (0.81 to 1.05)
Zhang28	Rectal	31–60 days	0.97 (0.89 to 1.06)	0.84 (0.70 to 1.01)
Zhang28	Rectal	>60 days	0.88 (0.80 to 0.97)	0.84 (0.68 to 1.03)
Wang27	Colon	No use	Reference	Reference
Wang27	Colon	Any use	2.31 (2.12 to 2.52)	0.94 (0.79 to 1.12)
Wang27	Colon	Lowest tertile of number of prescriptions	3.77 (3.39 to 4.20)	0.90 (0.75 to 1.08)
Wang27	Colon	Second tertile of number of prescriptions	1.90 (1.67 to 2.16)	0.99 (0.82 to 1.20)
Wang27	Colon	Highest tertile of number of prescriptions	1.27 (1.10 to 1.46)	0.77 (0.63 to 0.94)
Wang27	Rectal	No use	Reference	Reference
Wang27	Rectal	Any use	1.69 (1.50 to 1.90)	0.93 (0.76 to 1.14)
Wang27	Rectal	Lowest tertile of number of prescriptions	2.47 (2.13 to 2.86)	0.88 (0.71 to 1.09)
Wang27	Rectal	Second tertile of number of prescriptions	1.35 (1.13 to 1.62)	0.99 (0.80 to 1.23)
Wang27	Rectal	Highest tertile of number of prescriptions	1.10 (0.91 to 1.35)	0.82 (0.65 to 1.05)
Dik29	CRC	No use	Reference	Reference
Dik29	CRC	1–2 prescriptions	1.12 (1.03 to 1.23)	1.08 (0.99 to 1.18)
Dik29	CRC	3–4 prescriptions	1.27 (1.02 to 1.58)	1.01 (0.90 to 1.13)
Dik29	CRC	5–7 prescriptions	n/a	1.09 (0.95 to 1.25)
Dik29	CRC	8 or more prescriptions	n/a	1.25 (1.08 to 1.45)
Dik29	CRC	5 or more prescriptions	1.45 (1.07 to 1.97)	n/a

CRC, colorectal cancer; ES, effect size; n/a, not available.