Natural History of Helicobacter pylori Infection in Mexican Schoolchildren: Incidence and Spontaneous Clearance

Objectives: The aim of the present study was to estimate the incidence and spontaneous clearance rate of Helicobacter pylori infection and the effect of some variables on these outcomes in schoolchildren. Methods: From May 2005 to December 2010, 718 schoolchildren enrolled in 3 public boarding schools in Mexico City participated in the follow-up. At the beginning of the study and every 6 months thereafter, breath samples were taken to detect H pylori infection; blood samples and anthropometric measurements were taken to evaluate nutritional status. Data on sociodemographic characteristics were collected. Results: The prevalence of H pylori infection was 38%. The incidence rate was 6.36%/year. Schoolchildren with anemia or iron deficiency at the beginning of the study (who received iron supplements) showed a higher infection acquisition rate than those with normal iron nutritional status, hazard ratio (HR) 12.52 (95% confidence interval [CI] 4.01%-39.12%), P<0.001 and HR 2.05 (95% CI 1.09%-3.87%), P = 0.027, respectively. The spontaneous clearance rate of the infection was 4.74%/year. The spontaneous clearance rate was higher in children who had iron deficiency (who received iron supplements), HR 5.02 (95% CI 1.33%-18.99%), P = 0.017, compared with those with normal nutritional iron status. It was lower in schoolchildren with >= 2 siblings compared with schoolchildren with 1 or no siblings, HR 0.23 (95% CI 0.08%-0.63%), P = 0.004. Conclusions: H pylori infection status is dynamic in schoolchildren. Variables related to health status and infection transmission, such as iron status and number of siblings, are important for the incidence and spontaneous clearance of H pylori infection.