title: Meat intake and non-Hodgkin lymphoma: a meta-analysis of observational studies.
abstract: OBJECTIVE
  High intake of meat has been inconsistently associated with increased risk of non-Hodgkin lymphoma (NHL). We carried out a meta-analysis to summarize the evidence of published observational studies reporting association between red meat and processed meat intake and NHL risk.
  
  
  METHODS
  Analytical studies reporting relative risks with 95 % confidence intervals (95 % CI) for the association between intake of red and/or processed meat and NHL or major histological subtypes were eligible. We conducted random-effects meta-analysis comparing lowest and highest intake categories and dose-response meta-analysis when risk estimates and intake levels were available for more than three exposure classes.
  
  
  RESULTS
  Fourteen studies (four cohort and ten case-control) were included in the meta-analysis, involving a total of 10,121 NHL cases. The overall relative risks of NHL for the highest versus the lowest category of consumption were 1.14 (95 % CI 1.03, 1.26) for red meat and 1.06 (95 % CI 0.98, 1.15) for processed meat. Significant associations were present when the analysis was restricted to case-control studies but not when restricted to cohort studies. No significant associations were found for major NHL etiological subtypes. Dose-response meta-analysis could be based only on eight studies that provided sufficient data, and compared to no meat consumption, the overall NHL relative risk increased nonlinearly with increased daily intake of red meat.
  
  
  CONCLUSIONS
  The observed positive association between red meat consumption and NHL is mainly supported by the effect estimates coming from case-control studies and is affected by multiple sources of heterogeneity. This meta-analysis provided mixed and inconclusive evidences on the supposed relationship between red and processed meat consumption and NHL.
authors.affiliation: Department of Public Health and Infectious Diseases, Sapienza University of Rome, Piazza A. Moro 5, 00185, Rome, Italy. angelo.solimini@uniroma1.it.
authors.forename: Angelo G
authors.initials: AG
authors.lastname: Solimini
authors.affiliation: Department of Public Health and Infectious Diseases, Sapienza University of Rome, Piazza A. Moro 5, 00185, Rome, Italy.
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Lombardi
authors.affiliation: Department of Public Health and Infectious Diseases, Sapienza University of Rome, Piazza A. Moro 5, 00185, Rome, Italy.
authors.forename: Caterina
authors.initials: C
authors.lastname: Palazzo
authors.affiliation: Department of Public Health and Infectious Diseases, Sapienza University of Rome, Piazza A. Moro 5, 00185, Rome, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: De Giusti
mesh_terms: D016022:Case-Control Studies; D015331:Cohort Studies; D006801:Humans; D008228:Lymphoma, Non-Hodgkin / Q000453:epidemiology* / Q000209:etiology; D008460:Meat / Q000009:adverse effects*; D064887:Observational Studies as Topic; D012306:Risk
keywords: Dose–response meta-analysis; Non-Hodgkin lymphoma; Processed meat; Red meat