Scientists have long explored the link between the gut and the brain. Now, a new study shows that older adults with chronic inflammation of the digestive tract may develop dementia more than seven years earlier than those who do not have the condition.
A team of scientists at the University of California San Francisco and Taipei Veterans General Hospital in Taiwan has revealed that people with gut conditions, such as inflammatory bowel disease, have double the risk of dementia.
Previous studies have tied gut health to various conditions, particularly those affecting the brain. Mental health issues, developmental problems, and degenerative conditions have been associated with impaired gut health. This new study adds to a growing body of evidence on the reciprocal communication between the nervous system and the gut, known as the "gut-brain axis."
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What is inflammatory bowel disease (IBD)?
Inflammatory bowel disease (IBD) is an umbrella term describing two digestive conditions – Crohn's disease and ulcerative colitis. These conditions are characterized by chronic inflammation of the gastrointestinal (GI) tract. Prolonged inflammation may result in damage to the stomach, small intestine, and large intestine.
The most common signs and symptoms of IBD include recurring or bloody diarrhea, weight loss, pain or cramps in the abdominal area, and fatigue.
In 2015, an estimated 1.3% of US adults (3 million) reported being diagnosed with IBD (either Crohn's disease or ulcerative colitis). The exact cause of these two conditions is still unclear, but they were believed to root from dysregulated immune response to changes in the gut microbiome.
Increased risk of dementia
To arrive at their findings, the team used the Taiwanese National Health Insurance Research Database and conducted a comparative analysis of 1,742 patients with IBD who are more than 45 years old against 17,420 controls to assess dementia risk after being diagnosed with IBD. All the participants were followed for dementia diagnosis for up to 16 years.
The study, which was published in the journal Gut, involved more than 19,000 Taiwanese patients. The researchers found that those with inflammatory bowel disease (IBD) began manifesting symptoms of dementia after the age of 76, compared to the average onset in healthy people at age 83.
Also, the team found that the rate of dementia diagnosis was about four times higher in patients with IBD compared to the control group. After accounting for other factors such as age and underlying health conditions, people with IBD were more than twice more likely to develop dementia than those who had no IBD.
"Our findings suggest there may be an intimate connection between IBD and neurocognitive decline. Interestingly, we also found that dementia risk appeared to accelerate over time, correlating with the chronicity of IBD diagnosis," Dr. Bing Zhang, lead author and clinical gastroenterology fellow at UCSF, said.
Intestinal homeostasis depends on the complex interactions between the gut microbiome, the host immune system, and the intestinal epithelium. It has been tied to many mental and neurological disorders due to the signaling that happens between the gut and the central nervous system.
It was found that anxiety and depression are prevalent in about 20 to 30 percent of patients with IBD. Further, people with IBD with anxiety and depression had a higher risk of a flareup and worse outcomes when it comes to their psychiatric symptoms.
"As surprising as it may be, current research suggests the gut and the brain are linked through what is termed the gut-brain axis. The brain doesn't operate in isolation from the rest of the body, and inflammation plays a role in the development of diseases like Alzheimer's that cause dementia," Dr. Rosa Sancho, head of research at Alzheimer's Research UK, said.
The team noted that the study findings show that the gut-brain axis may be a factor in the development of dementia. They added that the connection might be due to the disruption of the intestinal epithelial barrier and the microbiome imbalance tied to IBD, assisting the passage of gut microbial-derived neurotoxic metabolites into the central nervous system.
Further research is still needed, particularly on the link between IBD and dementia. The findings of the study may pave the way for the development of new therapies and treatments that may prevent dementia.
"Early recognition of dementia and timely medical care through a multidisciplinary approach that includes support and education could slow cognitive deterioration and improve the quality of life for both the patient and their caretakers. However, diagnosis for this insidious syndrome requires vigilance and awareness," Zhang said.
- Zhang, B., Wang, H., Bai, Y.M. Tsai, S.J., Su, T.P., Chen, T.J., Wang, Y.P., and Chen, M.H. (2020). Inflammatory bowel disease is associated with higher dementia risk: a nationwide longitudinal study. Gut. https://gut.bmj.com/content/early/2020/04/28/gutjnl-2020-320789