New research from Karolinska Institutet demonstrates a link between inflammatory bowel disease and faster cognitive decline among dementia patients. The study, which is published in the scientific journal Gut, indicates a need for personalised treatments, researchers say.
"Our results indicate that inflammatory bowel disease (IBD) can worsen cognitive function in people with dementia," says principal investigator Hong Xu , assistant professor at the Department of Neurobiology, Care Sciences and Society at Karolinska Institutet in Sweden. "This opens the door to more effective care strategies with closer monitoring and targeted treatment, which will hopefully be able to improve the quality of these individuals' lives."
The bowel can affect the brain
Much has been written about the link between the gastrointestinal tract and the brain in recent years. There are hypotheses that IBD, such as Crohn's disease or ulcerative colitis, can contribute to dementia, but it remains a mystery how these diseases affect cognitive function.
For this present study, the researchers used the Swedish register for cognitive/dementia disorders (SveDem) to identify individuals who developed IBD after having been diagnosed with dementia. A total of 111 individuals with both dementia and newly diagnosed IBD were compared with 1,110 matched individuals with dementia but without IBD. Both groups were similar in terms of age, gender, type of dementia, comorbidity and ongoing medication.
The researchers analysed changes in MMSE (Mini-Mental State Examination) score, which is a common measure of cognitive function over time, and compared the rates of impairment between the two groups. They also studied how their MMSE scores changed before and after IBD diagnoses in the first group.
Faster cognitive decline
People with both dementia and IBD experienced a more rapid cognitive decline, with the impairment being more pronounced after their IBD diagnosis than before. People with both diagnoses lost almost 1 MMSE point more per year compared to those with dementia only.
"This decline is clinically significant and comparable with the difference between patients who are taking the new Alzheimer's drug donanemab and those who aren't," says Dr Xu. "More research is needed if we're to understand how inflammatory bowel diseases affect the brain and if treating IBD can slow down cognitive decline."
Since this was an observational study, no causalities can be established. The researchers also lacked information on the severity of the participants' IBD and had only limited information on how they were being treated for it.
The study was financed by several funding bodies, including the Swedish Research Council, StratNeuro, the Centre for Innovative Medicine (CIMED), The U&L Angeby Foundation, the Petrus and Augusta Hedlund Foundation, the Åke Wiberg Foundation, the Magnus Bergvall Foundation, the Swedish Kidney Foundation and Karolinska Institutet's foundations. There are no reported conflicts of interest.
Publication
" Inflammatory Bowel Disease Linked to Accelerated Cognitive Decline in Individuals with Dementia: A Nationwide Cohort Study ", Minjia Mo, Jiangwei Sun, Iris Mikulic, Jonas F. Ludvigsson, Sara Garcia-Ptacek, Maria Eriksdotter, Hong Xu, Gut, online 12 July 2025, doi: 10.1136/gutjnl-2025-335370.
