To Örebro University

BACKGROUND & AIMS: Microscopic colitis is one of the most common causes of chronic diarrhea in older populations. We investigated all-cause and cause-specific mortality in patients with microscopic colitis.

METHODS: We conducted a nationwide cohort study of all cases of microscopic colitis (n = 14,333) diagnosed from 1990 through 2017 in Sweden. Cases of microscopic colitis were identified using SNOMED codes from gastrointestinal histopathology reports collected from Sweden's 28 pathology departments. Each case of microscopic colitis was matched to 5 population comparators (n = 68,700). Mortality data were ascertained from Sweden's cause of death register. We used Cox proportional hazards modeling to estimate adjusted hazard ratios (aHRs) and 95% CIs.

RESULTS: Through December of 2017, we confirmed 3014 deaths in patients with microscopic colitis (27.4/1000 person-years) and 12,534 deaths in matched population comparators (23.3/1000 person-years). This corresponded to a 10-year absolute risk difference of 3.4% (95% CI, 2.1%-4.6%) and an aHR of 1.17 (95% CI, 1.12-1.22). However, further adjustment of models for comorbidity burden reduced the relative risk of death for patients with microscopic colitis (aHR, 0.98; 95% CI, 0.94-1.02). In analyses of cause-specific death, microscopic colitis was associated with an increased risk of gastrointestinal-related death (aHR, 1.68; 95% CI, 1.38-2.05) and infection-related death (aHR, 1.42; 95% CI, 1.11-1.83), but not cancer-related death (aHR, 0.83; 95% CI, 0.76-0.91) or cardiovascular-related death (aHR, 1.02; 95% CI, 0.96-1.10).

CONCLUSIONS: In a nationwide cohort study in Sweden, we found that patients with microscopic colitis were at increased risk of death. However, the increase appears to be related to higher burden of comorbidities in this population.