The occurrence of microscopic colitis in Sweden has risen steadily over the past decades, according to a new study from Karolinska Institutet published in Clinical Gastroenterology and Hepatology. The findings show that the disease is more common than previously recognised and affects mainly older adults, especially women.
Microscopic colitis is an inflammatory bowel disease that causes long lasting, watery diarrhoea. Because the bowel often looks normal during a colonoscopy, tissue samples are needed to diagnose the condition.
In the new study, the researchers have examined all individuals in Sweden diagnosed with microscopic colitis between 1995 and 2021. In total, 22,519 people had biopsy-verified disease.
"The results show a clear and sustained increase throughout the entire study period. The prevalence rose rapidly until the mid-2000s, and then continued to rise, although at a slower pace," says David Bergman , David Bergman, GP and researcher at the Department of Medical Epidemiology and Biostatistics and first author of the study.
In 2000, 6 out of every 100,000 women were diagnosed with microscopic colitis for the first time (incidence), compared to 2.5 out of every 100,000 men. By 2020, the incidence had risen to 24 per 100,000 women per year, and around 10 per 100,000 men, representing a fourfold increase in both sexes.
To understand whether the increase was due to more people being examined rather than more people actually developing the disease, the researchers compared trends in microscopic colitis with trends in biopsies showing normal mucosa. Both increased, but normal mucosa did so more slowly. According to the researchers, this may indicate a real increase in the disease or that healthcare has gradually identified people who were ill but previously undiagnosed.
The majority are older and women
In 2021, 170 individuals per 100,000 inhabitants in Sweden had been diagnosed with microscopic colitis. The lifetime risk is estimated at 1 in 54 for women and 1 in 133 for men. The majority of those affected were over 60 years of age at the time of diagnosis, and 71 per cent were women.
"Our results show that microscopic colitis is more common than previously thought, making it all the more crucial for healthcare professionals and patients to be aware of the disease. Its symptoms are often mistaken for other gastrointestinal disorders," says Jonas F. Ludvigsson , professor at the Department of Medical Epidemiology and Biostatistics, paediatrician in Örebro and senior author of the study.
"Our study cannot explain why the disease is increasing, but we have several ongoing projects to investigate the underlying causes," he adds.
The study was conducted using data from all 28 pathology laboratories in Sweden and was funded by the Karolinska Institutet, Region Stockholm, the Swiss National Science Foundation, the Swedish Society for Medical Research and the European Crohn's and Colitis Organisation. Several of the researchers report having received funding from pharmaceutical companies; details are provided in the scientific article.
David Bergman will present the study at Digestive Disease Week (DDW) 2026, held in the Chicago on 4 May. DDW is one of the world's largest scientific meetings for gastrointestinal research, bringing together clinicians, researchers and industry to share new findings on digestive diseases and related treatments.
Publication
"Increasing incidence and prevalence of Microscopic Colitis in Sweden: A nationwide population-based cohort study" , David Bergman, Soran Rabin Bozorg, Anders Forss, Jiangwei Sun, Carole A. Marxer, Darrell S. Pardi, Jonas F Ludvigsson, Clinical Gastroenterology and Hepatology, online May 5, 2026, doi: 10.1016/j.cgh.2026.03.019
