Associations between body mass index and gastroesophageal cancer incidence and mortality: novel insights from a nationwide registry-based cohort study.

The association between body mass index (BMI) and cancers of the esophagus and the stomach remains complex and requires further exploration. This study aimed to investigate this association, including early-onset (< 50 years) cancer and cancer related mortality. A nationwide registry-based cohort study was performed by linking data from multiple national registries in Norway. The cohort included 1,723,692 individuals, with 22,473 gastroesophageal cancer cases identified over 55,701,169 person-years of follow-up. In men, a 5 kg/m2 increase in BMI was associated with an increased risk of esophageal (HR 1.34, 95%CI 1.22-1.48) and cardia adenocarcinoma (HR 1.36, 95% CI, 1.22-1.50). This finding extended to individuals with high BMI in early life (16-29 years) for esophageal adenocarcinoma. The highest risk per 5 kg/m2 increase in BMI was observed for early-onset esophageal (HR 2.49, 95%CI 1.23-5.02) and cardia adenocarcinoma (HR 2.26, 95%CI 1.19-4.27). Among women, increased BMI was associated with a higher risk of both esophageal (HR 1.28, 95%CI 1.13-1.44) and gastric adenocarcinoma (HR 1.04, 95%CI 1.01-1.07). Women with elevated BMI in early life also demonstrated increased risk for these cancers. In both sexes, a 5 kg/m2 increase in BMI was inversely associated with squamous cell carcinoma of the esophagus. No association was observed between BMI and risk of cancer-related mortality. This study highlights an elevated risk of gastroesophageal adenocarcinomas with increasing BMI, with notable sex, age, and site-specific variations. The findings also point to a heightened risk of early-onset esophageal and cardia adenocarcinoma in men with high BMI.