title: Prevalence and incidence of Helicobacter pylori Infection in a healthy pediatric population in the Lisbon area.
abstract: BACKGROUND
  Helicobacter pylori is mainly acquired in childhood. Although adult studies reported a high prevalence of H. pylori infection in Portugal, the actual rate in children remains unknown. This study aimed to determine the prevalence and the incidence of H. pylori infection in an asymptomatic pediatric population of the Lisbon area and to correlate prevalence with sociodemographic determinants.
  
  
  METHODS
  Helicobacter pylori infection was determined by stool antigen test in 844 asymptomatic children (age 0-15 years; 49.4% boys). For the incidence study, H. pylori-negative children in the prevalence study were followed-up every 6 months over a 3-year period.
  
  
  RESULTS
  The global prevalence of H. pylori infection was 31.6%, increasing with age (19.9, 37.0 and 51.5%, in age groups 0-5, 6-10, and 11-15, respectively), but was similar among genders (34.5% in boys and 28.4% in girls). Older age and attendance of nursery/kindergarten during preschool constituted independent risk factors. The overall estimated incidence was 11.6 per 100 child-years (CY). Although 47.5% of children acquired H. pylori infection before 5 years of age, the mean age of acquisition was 6.3. The incidence of infection was similar among the three age groups (11.5, 13.0, and 10.5 per 100 CY, in age groups 0-5, 6-10, and 11-15, respectively).
  
  
  CONCLUSIONS
  The prevalence of H. pylori infection in the Portuguese pediatric population is still high. Although this study confirmed that the highest acquisition rate occurs at young age, it showed that in high-prevalence populations, older children can also acquire H. pylori infection at a rate similar to that of young children.
authors.affiliation: Departamento de Doenças Infecciosas, Instituto Nacional Saúde Dr Ricardo Jorge, Lisboa, Portugal. monica.oleastro@insa.min-saude.pt
authors.forename: Mónica
authors.initials: M
authors.lastname: Oleastro
authors.forename: Ana
authors.initials: A
authors.lastname: Pelerito
authors.forename: Paulo
authors.initials: P
authors.lastname: Nogueira
authors.forename: João
authors.initials: J
authors.lastname: Benoliel
authors.forename: Andrea
authors.initials: A
authors.lastname: Santos
authors.forename: José
authors.initials: J
authors.lastname: Cabral
authors.forename: Ana Isabel
authors.initials: AI
authors.lastname: Lopes
authors.forename: Paulo Magalhães
authors.initials: PM
authors.lastname: Ramalho
authors.forename: Lurdes
authors.initials: L
authors.lastname: Monteiro
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D005260:Female; D016481:Helicobacter Infections / Q000453:epidemiology*; D016480:Helicobacter pylori / Q000302:isolation & purification*; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D011174:Portugal / Q000453:epidemiology; D015995:Prevalence