Processed meat consumption and stomach cancer risk: A meta-analysis

Background. The relationship between processed meat consumption and the risk of stomach cancer is controversial. We conducted a meta-analysis to summarize available evidence from cohort and case-control studies on this issue. Methods: We searched Medline for studies of processed meat consumption and stomach cancer published from January 1966 through March 2006. Random-effects models were used to pool the relative risks from individual studies. All statistical tests were two-sided. Results: Six prospective cohort studies (involving 2209 stomach cancer patients) and nine case-control studies (2495 case patients) were eligible for inclusion in the dose-response meta-analysis of processed meat consumption. The estimated summary relative risks of stomach cancer for an increase in processed meat consumption of 30 g/day, approximately half of an average serving, were 1.15 (95% confidence interval [CI] = 1.04 to 1.27) for the cohort studies and 1.38 (95% CI = 1.19 to 1.60) for the case-control studies. There was no statistically significant heterogeneity among the cohort studies (P = .42) or among the case-control studies (P = .19). In three cohort and four case-control studies that examined the association between bacon consumption and stomach cancer, the summary relative risk was 1.37 (95% CI = 1.17 to 1.61) for the highest versus lowest intake categories of bacon, without heterogeneity among these studies (P = .66). Conclusion: Increased consumption of processed meat is associated with an increased risk of stomach cancer. However, the possibility that the association may be confounded or modified by other factors cannot be ruled out.