title: Contribution of H. pylori and smoking trends to US incidence of intestinal-type noncardia gastric adenocarcinoma: a microsimulation model.
abstract: BACKGROUND
  Although gastric cancer has declined dramatically in the US, the disease remains the second leading cause of cancer mortality worldwide. A better understanding of reasons for the decline can provide important insights into effective preventive strategies. We sought to estimate the contribution of risk factor trends on past and future intestinal-type noncardia gastric adenocarcinoma (NCGA) incidence.
  
  
  RESULTS
  We developed a population-based microsimulation model of intestinal-type NCGA and calibrated it to US epidemiologic data on precancerous lesions and cancer. The model explicitly incorporated the impact of Helicobacter pylori and smoking on disease natural history, for which birth cohort-specific trends were derived from the National Health and Nutrition Examination Survey (NHANES) and National Health Interview Survey (NHIS). Between 1978 and 2008, the model estimated that intestinal-type NCGA incidence declined 60% from 11.0 to 4.4 per 100,000 men, <3% discrepancy from national statistics. H. pylori and smoking trends combined accounted for 47% (range = 30%-58%) of the observed decline. With no tobacco control, incidence would have declined only 56%, suggesting that lower smoking initiation and higher cessation rates observed after the 1960s accelerated the relative decline in cancer incidence by 7% (range = 0%-21%). With continued risk factor trends, incidence is projected to decline an additional 47% between 2008 and 2040, the majority of which will be attributable to H. pylori and smoking (81%; range = 61%-100%). Limitations include assuming all other risk factors influenced gastric carcinogenesis as one factor and restricting the analysis to men.
  
  
  CONCLUSIONS
  Trends in modifiable risk factors explain a significant proportion of the decline of intestinal-type NCGA incidence in the US, and are projected to continue. Although past tobacco control efforts have hastened the decline, full benefits will take decades to be realized, and further discouragement of smoking and reduction of H. pylori should be priorities for gastric cancer control efforts.
authors.affiliation: Center for Health Decision Science, Harvard School of Public Health, Boston, Massachusetts, United States of America. jyeh@hsph.harvard.edu
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Yeh
authors.forename: Chin
authors.initials: C
authors.lastname: Hur
authors.forename: Deb
authors.initials: D
authors.lastname: Schrag
authors.forename: Karen M
authors.initials: KM
authors.lastname: Kuntz
authors.forename: Majid
authors.initials: M
authors.lastname: Ezzati
authors.forename: Natasha
authors.initials: N
authors.lastname: Stout
authors.forename: Zachary
authors.initials: Z
authors.lastname: Ward
authors.forename: Sue J
authors.initials: SJ
authors.lastname: Goldie
mesh_terms: D000230:Adenocarcinoma / Q000145:classification / Q000453:epidemiology* / Q000382:microbiology / Q000473:pathology / Q000517:prevention & control; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003198:Computer Simulation; D016481:Helicobacter Infections / Q000453:epidemiology* / Q000382:microbiology / Q000628:therapy; D016480:Helicobacter pylori / Q000472:pathogenicity*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D018570:Risk Assessment; D012307:Risk Factors; D040242:Risk Reduction Behavior; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology / Q000639:trends*; D016540:Smoking Cessation; D000074606:Smoking Prevention; D013274:Stomach Neoplasms / Q000145:classification / Q000453:epidemiology* / Q000382:microbiology / Q000473:pathology / Q000517:prevention & control; D013997:Time Factors; D014481:United States / Q000453:epidemiology; D055815:Young Adult