I found a recent review (Gastroenterol 2015; 148: 719-31) regarding Helicobacter pylori (HP) of interest. David Graham explores the issue of HP eradication with regard to cancer and whether there are benefits to the infection that result in detrimental effects with HP eradication.
The potential mechanisms in which HP infection can increase the risk of gastric cancer are depicted in Figure 2; the most important:
- Inflammation induced by infection
- Genetic/epigenetic changes –> genetic instability in gastric epithelial cells
Lessons regarding eradication therapy:
- Sequential therapy has been shown in some studies to be effective/superior (in Italy) yet inferior in others (eg. Korea). “The results are explained entirely by differences in patterns of drug resistance, which typically were not assessed before studies were initiated.”
- Findings from many studies cannot be applied to other populations without resistance data.
Does HP infection reduce the risk of obesity or childhood asthma? Probably not.
- “Any claim that a major human pathogen also might provide a meaningful health benefit, and that plans to eradicate it should be reconsidered, is guaranteed to elicit interest from the press.”
- As a counter example, Dr. Graham notes “because 2 events are associated does not mean that one causes the other. For example, one study reported a correlation between the number of storks in Brandenburg, Germany, and the birth rate in Berlin.” [Backen MB. Harm. In: Bracken MB. Risk, chance, and causation. New Haven: Yale University Press, 2013; 108-09.]
- He notes that HP can both promote or inhibit acid secretion/acid reflux. Increased acid secretion with resultant esophageal disease could increase the risk of adenocarcinoma of the esophagus; however, “the risk of developing adenocarcinoma of the stomach remains higher than the risk of adenocarcinoma of the esophagus.” This indicates that if there is an increased esophageal cancer risk, eradication would still be favorable by lowering gastric cancer risk.
- Asthma: “overall, the studies do not support the hypotheses that increases in childhood asthma were related to the absence of H pylori.”
- Obesity: “A meaningful causative association between H pylori and obesity is unlikely.”
Take-home message: H pylori is a pathogen and should be treated as such.
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