Best epidemiological abstracts at ECCO’23

The association of antibiotic use and IBD has been previously described. The following two abstracts examined this link in the paediatric and adult populations.

Jawad and colleagues (DOP 20) studied the risk of developing paediatric-onset IBD (pIBD) after exposure to systemic antibiotics during the first five years of life. Patients <18 years old diagnosed with pIBD in Denmark between 1995 and 2018 in the National Patient Registry were identified and each was matched to ten healthy controls, yielding 1808 patients with pIBD [989 Crohn’s Disease (CD)/819 Ulcerative Colitis (UC)] and 17,234 matched controls. An increased risk of developing pIBD was associated with prescription of antibiotics during the first five years of life (HR 1.32, 95%CI 1.2–1.5, p<0.0001), and risk was further increased if the patient had four or more antibiotic prescriptions compared to no antibiotic prescription (HR 1.43, 95%CI 1.2–1.6, p<0.0001). Prescription of broad-spectrum antibiotics increased the risk of pIBD compared to prescription of only narrow-spectrum antibiotics (HR 1.19, 95%CI 1.0–1.4, p=0.04). When patients were stratified by IBD subtype, only CD was significantly associated with exposure to antibiotics (HR 1.43, 95%CI 1.2–1.7, p=0.0003).

Faye and colleagues also examined the association of antibiotic use and IBD but in an adult population (DOP 22). The Danish patient registry was used to assess the impact of antibiotic exposure, including dose–response, timing and antibiotic class, on the risk of IBD in all individuals aged ≥10 years. A population-based cohort of residents aged ≥10 years was established between 2000 and 2018. Incidence rate ratios (IRRs) for IBD following antibiotic exposure were calculated using Poisson regression. There were a total of 6,104,245 individuals, resulting in 87,112,328 person-years of follow-up, and 52,898 new cases of IBD. Antibiotic exposure was associated with an increased risk of IBD as compared with no antibiotic exposure for all age groups, with the increase being greatest among individuals aged 40–60 years or ≥60 years (age 10–40 years, IRR 1.28, 95% CI 1.25–1.32; age 40–60 years, IRR 1.48, 95% CI 1.43–1.54; age ≥60 years, IRR 1.47, 95% CI 1.42–1.53). The highest risk of developing IBD was seen 1–2 years after antibiotic exposure and after use of antibiotic classes often prescribed to treat gastrointestinal pathogens. The findings implicate microbiome alterations as a risk factor for the development of both UC and CD.

Environmental factors and their impact on IBD were presented in two digital oral presentations. Fantodji and colleagues analysed early life exposures and risk of IBD (DOP 24). The aim of this study was to estimate the associations between exposures in infancy (birth until 3 years of age), such as breastfeeding, antibiotic treatment, presence of domestic pets and passive smoking, and the occurrence of IBDs. This case-control study was nested within the Quebec Birth Cohort on Immunity and Health. Cases and controls among persons born in Quebec between 1970 and 1974 were identified on the basis of their health services from 1983 to 2014, using validated algorithms. All cases and randomly selected controls were invited to participate in a web or telephone questionnaire. Participation rates were 47% among controls (n=946) and 52% (n=1212) and 55% (n=570), respectively, among patients with CD and UC. Logistic regression models were used to estimate adjusted odds ratios (OR) and 95% CIs separately for CD and UC.

Adjusting for perinatal and sociodemographic characteristics, the risk for CD or UC did not differ between exclusively breastfed and non-breastfed subjects. Partial breastfeeding (breastfeeding combined with infant formula) was associated with an increase in the odds of UC (OR 1.40, 95% CI 0.99–1.99). Early introduction of solid foods was associated with higher odds of CD (introduction at 3–6 months compared with >6 months: OR 1.35, 95% CI 1.05–1.78) but not UC (OR 1.06, 95% CI 0.77–1.46). Antibiotic use and the presence of domestic pets were not associated with either CD or UC. Passive smoking was associated with increased odds of CD (OR 1.23, 95% CI 1.00–1.51) but not UC (OR 0.96, 95% CI 0.75–1.22). The authors concluded that early introduction of solid foods and passive smoking increases the risk of CD, whereas there is a trend towards increased risk of UC with partial as compared with no breastfeeding.

Banerjee and colleagues examined environmental exposures in a large cohort of patients with and without IBD in India with the aim of identifying key risk factors (DOP 60).  A detailed questionnaire-based survey of environmental risk factors, including diet, smoking, antibiotic use, hygiene status, microbial exposures, vaccination, water supply and rural/urban residence, was conducted prior to patients attending colonoscopy screening. The risk factors were compared among IBD and non-IBD patients with normal colonoscopy. Univariate logistic regression was done initially adjusting for age and sex followed by multivariate analysis to estimate adjusted odds ratios (aORs) and 95% CIs.

A total of 13421 patients completed the environmental risk questionnaire, among whom 1306 cases of IBD (576 CD,730 UC) were diagnosed. The 12115 patients with normal colonoscopy served as the controls. In a multivariate model, current smoking, ex-smoking, non-vegetarian diet, daily bakery/fast food consumption, soft drink consumption, delivery by caesarean section, antibiotic use (at <1 year of age), exposure to pets, Western toilets and childhood infections were associated with increased risk of UC and CD.  Breastfeeding for >6 months, daily fruit consumption and daily exercise were protective against both UC and CD. Rural habitat was not protective against development of either UC or CD. This large prospective study identified several factors which could modulate the risk of IBD in later life.