Exposure to a bacterium responsible for a widespread stomach infection has been associated with a notable percentage of bowel cancer cases, according to research.
Helicobacter pylori bacteria, commonly referred to as H. pylori, trigger a routine gastrointestinal bug.
While the majority of infections pass without symptoms, some patients develop ulcers or inflammation along the lining of their stomach.
A substantial number of people are believed to contract the bug during childhood, with transmission occurring through direct contact with an infected individual’s saliva, vomit or stool.
Although H. pylori is already an established cause of stomach cancer, researchers noted that its potential connection to bowel cancer remains "highly controversial" as they set out to evaluate the association.
Data from the charity Guts UK indicates that as many as two in five individuals across the UK carry H. pylori within their digestive system.
To investigate, an international group of experts co-led by academics at the University of Hong Kong and the University of California San Diego examined findings from extensive reviews of prior studies regarding germ exposure and bowel cancer, combining these with figures provided by 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.”
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