Autoimmune conditions and gastric cancer risk in a population-based study in the United Kingdom

BACKGROUND: Although overall incidence of gastric cancer is decreasing, incidence has been increasing among young people in some Western countries. This trend may stem from the increase in autoimmune conditions. METHODS: A nested case-control study of gastric cancer in UK Clinical Practice Research Datalink. Up to ten cancer-free controls were matched to cases by age and sex. Conditional logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CI) for associations between analyzable autoimmune conditions (n = 34) and gastric cancer with Bonferroni correction. We evaluated associations between pernicious anaemia and other conditions. A meta-analysis of published prospective studies and ours was conducted. RESULTS: Among 6586 cases (1156 cardia, 1104 non-cardia, and 4334 overlapping/unspecified tumours) and 65,687 controls, any autoimmune condition was associated with gastric cancer (OR = 1.10; 95% CI: 1.01-1.20). Individuals with pernicious anaemia had higher gastric cancer risk than those without (OR = 2.75; 2.19-3.44). Among controls, pernicious anaemia was associated with seven other conditions (OR range: 2.21-29.80). The pooled estimate for any autoimmune condition and gastric cancer was 1.17 (1.14-1.21; n = 47,126 cases). CONCLUSION: Autoimmunity increases gastric cancer risk. Some autoimmune conditions may be indirectly associated with gastric cancer via pernicious anaemia. Pernicious anaemia could be considered for gastric cancer risk stratification and screening.