Visceral obesity is associated with an increased risk of developing esophago-gastric junctional adenocarcinoma in Japan: a population-based case–control study in Akita Prefecture

Background: While an association between esophago-gastric junctional adenocarcinomas (EGJACs) and obesity, especially visceral obesity, has been suggested in Western countries, the association remains unclear in Asia, including Japan. In this population-based case–control study, we investigated the association between EGJACs and obesity. Methods: To perform near-population-based data collection for all early-stage EGJACs occurring in Akita Prefecture from 2014 to 2019, clinical data, including endoscopic and computed tomography (CT) findings, were collected from 11 cancer treatment base hospitals in the area. Age- and gender-matched controls were extracted at a case-to-control ratio of 1:2 from healthy subjects who received health checkups in the same area. The visceral fat area (VFA) was calculated using CT images. Logistic regression analyses were performed to investigate the associations between EGJACs and obesity-related parameters. Results: In total, 74 EGJAC cases (62 males, median age of 70 years old) and 148 controls were extracted. Multivariable analyses showed a significantly negative association between the BMI and EGJACs and a significantly positive association between the VFA and EGJACs with odds ratios (ORs) (95% confidence intervals [CIs]) of 0.65 (0.53–0.80) and 1.01 (1.01–1.02), respectively. These findings were confirmed in another dataset (40 EGJACs and 80 controls). In addition, as a categorical variable, VFA ≥ 100 cm² showed a significantly positive association with EGJACs (OR [95% CI] 1.96 [1.02–3.76]). Conclusions: We found paradoxical associations between EGJACs and obesity-related parameters (BMI vs. VFA) in a Japanese population, suggesting a potentially pivotal role of the VFA rather than the BMI as a risk factor for EGJACs.