Regional Variations In Helicobacter Pylori Infection, Gastric Atrophy And Gastric Cancer Risk: The Enigma Study In Chile

Background Regional variations in gastric cancer incidence are not explained by prevalence ofHelicobacter pylori, the main cause of the disease, with several areas presenting highH.pyloriprevalence but low gastric cancer incidence. The IARC worldwideH.pyloriprevalence surveys (ENIGMA) aim at systematically describing age and sex-specific prevalence ofH.pyloriinfection around the world and generating hypotheses to explain regional variations in gastric cancer risk. Methods We selected age- and sex-stratified population samples in two areas with different gastric cancer incidence and mortality in Chile: Antofagasta (lower rate) and Valdivia (higher rate). Participants were 1-69 years old and provided interviews and blood for anti-H.pyloriantibodies (IgG, VacA, CagA, others) and atrophy biomarkers (pepsinogens). Results H.pyloriseroprevalence (Age-standardized to world population) and antibodies against CagA and VacA were similar in both sites.H.pyloriseroprevalence was 20% among children <10 years old, 40% among 10-19 year olds, 60% in the 20-29 year olds and close to or above 80% in those 30+ years. The comparison of the prevalence of known and potentialH.pyloricofactors in gastric carcinogenesis between the high and the low risk area showed that consumption of chili products was significantly higher in Valdivia and daily non-green vegetable consumption was more common in Antofagasta. Pepsinogen levels suggestive of gastric atrophy were significantly more common and occurred at earlier ages in Valdivia, the higher risk area. In a multivariate model combining both study sites, age, chili consumption and CagA were the main risk factors for gastric atrophy. Conclusions The prevalence ofH.pyloriinfection and its virulence factors was similar in the high and the low risk area, but atrophy was more common and occurred at younger ages in the higher risk area. Dietary factors could partly explain higher rates of atrophy and gastric cancer in Valdivia. Impact The ENIGMA study in Chile contributes to better understanding regional variations in gastric cancer incidence and provides essential information for public health interventions.