# Microscopic colitis is associated with an increased risk of dementia in a Swedish population

## TL;DR

People with microscopic colitis may have a higher risk of developing dementia shortly after diagnosis, but this link fades over time.

## Contribution

This study is the first to show a short-term increased dementia risk in microscopic colitis patients using a large population cohort.

## Key findings

- Microscopic colitis was linked to a 19% higher dementia risk in the first 5 years after diagnosis.
- The increased risk was observed for both Alzheimer's and vascular dementia.
- A lower prevalence of prior dementia was found in microscopic colitis patients, suggesting possible underdiagnosis.

## Abstract

The microbiota–gut–brain axis has been implicated in dementia. Yet whether dementia is associated with microscopic colitis (MC), an age‐related inflammatory colonic disease involving gut dysbiosis, remains unknown.

Using the nationwide ESPRESSO cohort in Sweden, we compared MC patients histologically diagnosed 1990–2017 and aged ≥30 years to their population‐based comparators and siblings, separately. MC association with incident and prevalent dementia diagnosis, respectively, was investigated in a matched cohort and a matched case‐control design.

Following 13,037 MC patients and 61,710 population comparators for a median of ∼10 years, we observed 4674 incident dementia cases (46% were Alzheimer's disease [AD]). During the first 5 years since biopsy, MC was associated with a 19% higher dementia risk (adjusted hazard ratio [aHR]: 1.19; 95% confidence interval [CI]: 1.07–1.32). This short‐term association applied to both AD and vascular dementia and appeared stronger as compared to siblings (aHR: 1.55; 95% CI: 1.22–1.97). After 5 years, it attenuated to null in both comparisons, regardless of dementia subtype. Prior dementia was less prevalent in MC (adjusted odds ratio [aOR]: 0.73; 95% CI: 0.65–0.82). This inverse association was independent from medications commonly prescribed in MC but was not supported by sibling findings (aOR: 1.11; 95% CI: 0.81–1.51).

MC patients may be more vulnerable to dementia diagnosis in early disease course. The intriguing inverse association between MC and preexisting dementia implies a possible underdiagnosis of MC in demented population and warrants further investigation.