(233) Antibiotic use and risk of microscopic colitis in older adults: a nationwide self-controlled case series study

Background: Several drugs have been linked to microscopic colitis, a condition often diagnosed in response to chronic diarrhea that reduces quality of life. Antibiotics can induce similar symptoms, but it remains unknown if this is related to microscopic colitis.

Objectives: We aimed to investigate the antibiotics-related risks of microscopic colitis in adults aged 65 years and older.

Methods: A nationwide self-controlled case series study including adults aged ≥65 years with a new prescription of antibiotics, diagnosed with incident, biopsy-confirmed, microscopic colitis in Sweden, 2007–2017. We identified cases from the nationwide histopathology cohort ESPRESSO individually linked to several nationwide registers. We estimated the incidence rate ratio (IRR) of microscopic colitis with a conditional Poisson regression for four risk periods: on treatment, 1-14, 15-91 and 92-365-days post treatment, compared with the non-treatment periods in the same individual. Antibiotic duration was identified based on the prescribed daily dose, extracted via a text-parsing algorithm, and a 7-day grace period. We also conducted a negative control outcome analysis where individuals with biopsy-confirmed normal mucosa were regarded as cases to test the association between gastrointestinal workup and antibiotic use. Finally, we used E-values for quantitative bias assessment.

Results: We identified 2,441 persons with incident biopsy-confirmed microscopic colitis (median age at diagnosis 74 years), of whom 67% were females. The most common comorbidity was hypertension (28%). The most frequent co-prescribed drugs were lipid-modifying agents (41%) and beta blockers (40%). Compared with the non-treatment periods, the risk of microscopic colitis in the age-adjusted analysis increased on treatment (IRR: 1.27 [1.02 - 1.58], E-value: 1.86), 1-14 days (IRR: 1.37 [1.04 - 1.79], E-value: 2.07), 15-91 days (1.07 (0.91 - 1.24], E-value: 1.33) and 92-365 days post treatment (1.20 [1.08 - 1.33], E-value: 1.68). However, the negative control outcome analysis revealed similar risks of having a biopsy-confirmed normal mucosa after antibiotic use.

Conclusions: This nationwide study on adults aged ≥65 in Sweden shows that the potential link between antibiotic use and microscopic colitis is likely due to antibiotic treatment of non-specific gastrointestinal symptoms when patients undergo workup. This surveillance bias suggests that antibiotics use is not linked to the occurrence of microscopic colitis.