title: Early-life family structure and microbially induced cancer risk.
abstract: BACKGROUND
  Cancer may follow exposure to an environmental agent after many decades. The bacterium Helicobacter pylori, known to be acquired early in life, increases risk for gastric adenocarcinoma, but other factors are also important. In this study, we considered whether early-life family structure affects the risk of later developing gastric cancer among H. pylori+ men.
  
  
  RESULTS
  We examined a long-term cohort of Japanese-American men followed for 28 y, and performed a nested case-control study among those carrying H. pylori or the subset carrying the most virulent cagA+ H. pylori strains to address whether family structure predicted cancer development. We found that among the men who were H. pylori+ and/or cagA+ (it is possible to be cagA+ and H. pylori- if the H. pylori test is falsely negative), belonging to a large sibship or higher birth order was associated with a significantly increased risk of developing gastric adenocarcinoma late in life. For those with cagA+ strains, the risk of developing gastric cancer was more than twice as high (odds ratio 2.2; 95% confidence interval 1.2-4.0) among those in a sibship of seven or more individuals than in a sibship of between one and three persons.
  
  
  CONCLUSIONS
  These results provide evidence that early-life social environment plays a significant role in risk of microbially induced malignancies expressing five to eight decades later, and these findings lead to new models to explain these interactions.
authors.affiliation: Department of Medicine, New York University School of Medicine, New York, New York, United States of America. martin.blaser@med.nyu.edu
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Blaser
authors.forename: Abraham
authors.initials: A
authors.lastname: Nomura
authors.forename: James
authors.initials: J
authors.lastname: Lee
authors.forename: Grant N
authors.initials: GN
authors.lastname: Stemmerman
authors.forename: Guillermo I
authors.initials: GI
authors.lastname: Perez-Perez
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000907:Antibodies, Bacterial / Q000097:blood / Q000276:immunology; D000942:Antigens, Bacterial / Q000235:genetics; D001213:Asian / Q000706:statistics & numerical data; D001426:Bacterial Proteins / Q000235:genetics; D001722:Birth Order; D016022:Case-Control Studies; D015331:Cohort Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005190:Family; D005192:Family Health; D016481:Helicobacter Infections / Q000097:blood / Q000150:complications*; D016480:Helicobacter pylori / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007564:Japan / Q000208:ethnology; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D012307:Risk Factors; D013274:Stomach Neoplasms / Q000209:etiology*; D013997:Time Factors; D014774:Virulence / Q000235:genetics
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D007074:Immunoglobulin G; C080866:cagA protein, Helicobacter pylori