Socioeconomic Factors and Risk of Esophageal Adenocarcinoma: A Nationwide Swedish Case-Control Study

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Abstract
Background: The increase in esophageal adenocarcinoma incidence in developed countries remains unexplained. Although low socioeconomic status (SES) is linked to an increased risk of esophageal squamous cell carcinoma (SCC), the relation with adenocarcinoma is uncertain. Methods: We addressed the importance of various socioeconomic factors in a Swedish population-based case-control study, where 189 and 262 cases of esophageal adenocarcinoma and the gastric cardia, respectively, 167 cases of esophageal SCC, and 820 control participants underwent personal interviews. Our classification of SES was derived from occupational histories. Relative risks were estimated by odds ratios with 95% confidence intervals (95% CI), derived from conditional logistic regression, in crude and adjusted models. Results: The risk of both esophageal adenocarcinoma and SCC increased with decreasing SES; unskilled workers had 3.7-fold (95% CI, 1.7-7.7) and 2.1-fold (95% CI, 1.0-4.7) increased risks, respectively, compared with age- and sex-comparable professionals. Adjustment for reflux symptoms, body mass, and tobacco smoking attenuated the excess risk for esophageal adenocarcinoma, whereas adjustment for Helicobacter pylori infection in a subset of the interviewed participants did not influence the results. Life without a partner was associated with a >2-fold increased risk of both histologic types of esophageal cancer, associations that remained even after multiple adjustments. Conclusions: Esophageal adenocarcinoma and SCC are both linked to low SES and a life without a partner. These associations are only partly explained by established risk factors.