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

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. 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. 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). 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.