Table 2 ∣.

Clinical studies evaluating antibiotic exposure and inflammatory bowel disease

Study	Antibiotic exposure timing	Date (location)	Study design	Antibiotic data source	Disease diagnosis	Key findingsa
Kronman et al.150	Childhood	2012 (UK)	Retrospective cohort	Health records registry	Diagnosis (Read) codes	HR IBD 5.51 (1.66–18.28) — antibiotic exposure before 1 year of age; HR 2.62 (1.61–4.25) — by 5 years of age; HR 1.57 (1.35–1.84) — by 15 years of age Dose dependency
Hviid et al.151	Childhood	2011 (Denmark)	Retrospective cohort	National health registry	Diagnosis (ICD) codes	IBD RR 1.84 (1.08–3.15) Dose dependency
Nguyen et al.152	All	2020 (Sweden)	Case–control	National health registry	Diagnosis (ICD) codes	aOR IBD 1.94 (1.85–2.03) Dose dependency
Shaw et al.153	Infants <1 year of age	2010 (Manitoba, Canada)	Nested case–cohort	Provincial health registry	Diagnosis (ICD) codes	OR IBD 2.9 (1.2–7.0) Dose dependency
Shaw et al.154	2–5 years before diagnosis	2011 (Manitoba, Canada)	Case–control	Provincial health registry	Diagnosis (ICD) codes	aOR IBD 1.27 (1.20–1.35) Dose dependency
Card et al.157	2–5 years before diagnosis	2004 (UK)	Case–control	Research database	Diagnosis (Oxmis, Read) codes	aOR IBD (1.05–1.65) No dose dependency
Virta et al.158	Childhood	2012 (Finland)	Case–control	National health registry	Diagnosis (ICD) codes	aOR CD 1.87 (1.37–2.56) aOR UC 1.18 (0.92–1.52)
Ungaro et al.155	Variable	2014 (Europe, Canada, New Zealand)	Meta-analysis	Mostly health registries, some surveys	Varies	Pooled OR IBD 1.57 (1.27–1.94)
Zou et al.156	Childhood	2020 (North America, Eurasia, Oceania)	Meta-analysis	Varies	Varies	Pooled OR IBD 1.5 (1.22–1.85)

aOR, adjusted odds ratio; CD, Crohn’s disease; IBD, inflammatory bowel disease; ICD, international Classification of Disease; RR, rate ratio; UC, ulcerative colitis.

^aValue ranges in parentheses are 95% confidence intervals.