Proton pump inhibitors and gastric cancer: association is not causation

• Published in: Gut Vol. 68; no. 8; pp. 1529 - 1530
• Main Authors: Moayyedi, Paul, Veldhuyzen van Zanten, Sander J O, Hookey, Lawrence, Armstrong, David, Jones, Nicola, Leontiadis, Grigorios I
• Format: Journal Article
• Language: English
• Published: England BMJ Publishing Group LTD 01.08.2019
• Subjects: Anti-Ulcer Agents; Gastric cancer; Gastroenterology; Helicobacter pylori; Humans; Proton Pump Inhibitors; Stomach Neoplasms; Canada; epidemiology; proton pump inhibition; gastric adenocarcinoma
• ISSN: 0017-5749; 1468-3288
• DOI: 10.1136/gutjnl-2018-316958

The main problem for all database studies evaluating the risks of PPI is that none was specifically created to assess PPI-related events. [...]many confounders, such as socioeconomic status or comorbidities, are not recorded in sufficient detail to allow for adequate adjusting in a multivariate model. Furthermore, sicker patients are more likely to develop additional illnesses, and this is the explanation that PPIs have been associated with an ever-increasing number of diseases.2 A careful evaluation of the data would suggest that most, if not all, of these presumed PPI associations are attributable to residual confounding.3 It is noteworthy that the authors’ adjustment for confounders produced modest attenuation of the HR. More dramatic risk reductions have been reported by other authors after adjusting for confounders in similar studies.3 Cheung et al conducted a propensity-matched analysis as this can partially adjust for unknown and known confounders, but this approach is only as good as the underlying dataset and it can have many inherent biases.4 In this case, the approach is likely to be flawed as the HR actually increases with the trimmed results and is similar to the univariate analysis.