Common germ linked to large number of bowel cancers in new study
Most infections, which are spread through contact with an infected person’s vomit, stool or saliva, do not cause symptoms, but some people will experience ulcers or inflammation of the stomach lining
Being exposed to a germ that causes a common stomach infection has been linked to a significant proportion of bowel cancers in a new study.
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Helicobacter pylori bacteria, also known as H. pylori, can lead to helicobacter pylori infection – a common stomach bug.
Most infections do not cause symptoms, but some people will experience ulcers or inflammation of the stomach lining.
A significant proportion of people are estimated to have had this infection, often in childhood, which is spread through contact with an infected person’s vomit, stool or saliva.
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H. pylori is a known cause of stomach cancer but the relationship between H. pylori and bowel cancer remains “highly controversial”, experts said as they set out to explore the potential link.
According to Guts UK, up to two in five people in the UK have H. pylori in their stomach.
An international team of experts, led by researchers from the University of Hong Kong and the University of California San Diego, analysed data from large reviews of previous studies on germ exposure and bowel cancer and combined it with estimates from the Global Cancer Observatory.
The analysis found that exposure to H. pylori is linked to a 1.59-fold increased risk of bowel cancer, compared to not being exposed to the bacteria.
And using data from 43 studies, which involved more than 48 million people, they estimated that 22% of bowel cancer cases worldwide are potentially related to H. pylori exposure.
Only four studies included in the analysis looked H. pylori “eradication” with antibiotics and continued cancer risk, these suggested that clearing the infection could reduce bowel cancer risk, but only after 10 years.
The researchers also examined data on the proportion of bowel cancers linked to infection based on when people were born, with three age brackets included in the study – those born before 1947; between 1948 and 1962; and people born between 1963 and 1977.
H. pylori exposure was linked to 9.5% of bowel cancers among the oldest group studied, 10.2% of bowel cancers among those born between 1948 and 1921 and 15% of bowel cancers for those born between 1963 and 1977.
“H. pylori exposure may be related to an estimated 22% of global CRC (colorectal cancer) cases under a causal assumption, the authors wrote in the journal eGastroenterology.
“These findings may inform primary CRC prevention strategies, particularly in regions with high H. pylori prevalence and limited resources.
“However, high-quality, prospective studies with long-term follow-up are warranted to clarify whether H. pylori eradication causally reduces CRC risk.”
Genevieve Edwards, chief executive of Bowel Cancer UK, said: “Every 11 minutes someone in the UK is diagnosed with bowel cancer, making it the UK’s fourth most common cancer.
“This study’s conclusion that exposure to Helicobacter pylori may be associated with more than one in five cases of bowel cancer worldwide could go some way to helping us understand why people develop the disease.
“We always welcome further research into the potential risk factors of bowel cancer, and the findings of this study are worth exploring further. We look forward to seeing more studies into this area of concern.”