title: Systematic review of the prevalence of gastric intestinal metaplasia and its area-level association with smoking.
abstract: OBJECTIVE
  We aimed to show an area-level association between the frequency of intestinal metaplasia (IM) in Helicobacter pylori-infected patients and tobacco consumption.
  
  
  METHODS
  We systematically reviewed the literature to retrieve data on the prevalence of IM in different countries and performed an ecological analysis to quantify the association between the prevalence of IM among infected subjects and smoking, using data on national tobacco availability. Articles evaluating IM in the general population or in dyspeptic patients were identified by a MEDLINE search. We selected one study per country, giving preference to those for which the study design/populations evaluated provided the highest external validity and inter-study comparability of methodology.
  
  
  RESULTS
  This systematic review of published data retrieved information for 29 countries from 5 continents depicting a wide variation in the prevalence of IM among H. pylori-infected subjects in different regions, ranging from 3% in Argentina to 55% in New Zealand. In countries exhibiting a simultaneously high prevalence of infection and low incidence of gastric cancer, IM was also relatively infrequent (Thailand, 6%; India, 8.2%; Nigeria, 11.1%; Gambia, 11.8%; Saudi Arabia, 15.5%; Iran, 15.6%; Egypt, 24.4%). A significant correlation was observed between IM prevalence in infected subjects and tobacco availability (r = 0.45; p = 0.02).
  
  
  CONCLUSIONS
  Our results show that the concept of the African and Asian "enigmas" may be extended to precancerous lesions. Tobacco availability was positively associated with the prevalence of IM among H. pylori-infected subjects at an area level.
authors.affiliation: Department of Hygiene and Epidemiology, University of Porto Medical School, Porto, Portugal.
authors.forename: Bárbara
authors.initials: B
authors.lastname: Peleteiro
authors.forename: Joana
authors.initials: J
authors.lastname: Bastos
authors.forename: Henrique
authors.initials: H
authors.lastname: Barros
authors.forename: Nuno
authors.initials: N
authors.lastname: Lunet
mesh_terms: D016481:Helicobacter Infections / Q000150:complications* / Q000473:pathology*; D016480:Helicobacter pylori; D006801:Humans; D007422:Intestines / Q000473:pathology*; D008679:Metaplasia / Q000453:epidemiology / Q000473:pathology; D015995:Prevalence; D012907:Smoking / Q000009:adverse effects*