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

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.