Published: 24-05-2022 08:58 | Updated: 25-05-2022 14:46

Epidemiology of microscopic colitis – risk of associated disorders and death

Microscopic colitis is the most recently recognized inflammatory condition of the large intestine in which abnormal reactions of the immune system cause inflammation of the inner lining of the colon. At present, more than 10,000 people in Sweden are estimated to be living with the disease. Previously, insufficient awareness and knowledge of microscopic colitis have led to underdiagnosis of the disorder, leaving patients untreated.

Common symptoms include chronic, watery diarrhea and the disease is more common in older adults and in women, but anyone can develop microscopic colitis. Most likely genetic factors and abnormal immune reactions play a role in disease development.

As the term microscopic implies, a microscopic evaluation of a tissue biopsy from the large intestine is required to establish a diagnosis of microscopic colitis. Therefore, access to colonoscopy and knowledge of the typical histopathological findings are required in the diagnostic process.

Further, missed diagnoses due to insufficient awareness have hampered the ability of researchers to conduct large-scale studies on prognosis, associated disorders and outcomes.

In his thesis, Dr David Bergman at the Department of Medical Epidemiology and Biostatistics aimed to assess the reliability of data from Swedish pathology registers for identifying patients with microscopic colitis. In his studies, he also examined the incidence of microscopic colitis between 1995 and 2015. David further assessed the risks of death and cancer in patients with microscopic colitis and also the risk of later microscopic colitis in patients with celiac disease.

What are the most important results in your thesis?

–Our studies confirm a high accuracy regarding microscopic colitis in Swedish pathology registries. Our incidence study reveals a substantial increase of microscopic colitis during the past decades, but with stabilizing rates from 2010–2015. We also saw that patients with microscopic colitis are at an increased risk of death. However, it seems that the increased mortality is associated with other disorders occurring at the same time and not with microscopic colitis in itself. We also found a modestly (+8%) increased risk of cancer in patients with microscopic colitis. It is possible that this risk is partly due to an increased surveillance of these patients. Finally, we showed that patients with celiac disease are at an elevated risk of developing microscopic colitis.

Why did you choose to study this particular area?

–With microscopic colitis being a relatively recently recognized disease, I felt that the Swedish health registers provided us with a unique opportunity to enhance knowledge of this disease.

What do you think should be done moving forward in this research area?

–There are a lot of things that we do not know about microscopic colitis. For example, smokers are at an increased risk of developing MC and as smoking has a negative effect on health in many ways it is difficult to separate the effect of microscopic colitis from the effect of smoking on, for example, cancer. Therefore, it would be valuable if data on smoking habits could be gathered and made accessible for researchers. Also, I think that similar studies as the ones we have performed from countries with a different panorama of risk factors would be an interesting addition.

Doctoral thesis

Microscopic colitis: epidemiology, death and associated disorders.

David Bergman. Karolinska Institutet (2022), ISBN: 978-91-8016-582-2